It's not hard to make a new timeline, any number of small changes in a primary timeline can result in an offshoot. Recreating a timeline though after it's been destroyed is rather difficult. First you have to track down the original spawning event, the genesis. Why did that timeline come into being? Often when a timeline is wiped out it's not completely rather it's more like shattering a glass vase. You can see the base and the first couple events and most of the primary timeline is still bleeding through into it. Once you progress out to where the damage is it's usually too many conflicting events or overlap with other timelines, often you need to create supports for a given event to recreate what was supposed to happen there.
When you've stepped into a destroyed timeline you can see all possible events occurring simultaneously everywhere. Often it looks like one giant blur. There's also bleed through from other timelines happening and certain things just don't behave like you normally expect them to. Sometimes solids behave like gasses or the gravity is different, cars drive on roads that don't exist or weird angles, sometimes even sideways. It's much like a horribly glitched video game. Worse still is the fact that all these things are constantly changing all the time which can make it astoundingly disorienting. Things will change colors, you can feel things moving, shifting, changing, and it makes it hard to balance yourself. Often it's so bad you'll almost immediately vomit and will be sick the entire time you're there until you start to stabilize it. A fact made more difficult by the nature of the timeline you're in. The best option actually is to reinforce the genesis point, think of it if you will as a root. Once you make the genesis a stronger event, making so it's forced to happen can often recreate significant portions of a destroyed timeline. Often timelines are only destroyed as far back as the disrupting event has force. That is to say then that no timeline is ever truly lost, merely pushed aside by a stronger force. Often the natural occurrences of this are due to strong time events on a primary timeline and of course this usually destroys the genesis which is why the whole timeline can be lost. Though it may still be possible to find even in that scenario. Though likely if you're reading this with serious intent then it's because an unnatural disturbance destroyed the timeline in question and you want to know how to fix it. The simple answer to that is to find the epicenter of the disturbance, understand the nature of it and then correct it accordingly. For example if you made too many changing conflicts in an area at a time and it's upset everything then you need to stop yourself from interfering.
It's hard to know exactly what will destabilize a timeline in progress, though it's not hard to disturb a timelines future it's usually not so destructive to wipe out the entire past of the timeline as well. Though a sudden lack of strong events could be said be said to be one cause in that there's nothing to give the timeline order and thus it just goes wild. Similarly it could be said too many strong events in an area tear it apart. In particular if you're setting up two strong events that essentially conflict with each other by nature they tend to either neutralize each other or have a compound effect neither of which tend to play nicely with the timeline. Often a neutralization event where they cancel each other out works like an implosion sometimes taking out other strong time events which in the end can make a distinctive lack of order in a timeline. While the compound effect is trying to separate the timeline in two when it has no implicit reason to do so as there's no alternative events occurring. This is when it tends to explode and fragment the timeline. A destroyed timeline the closer you get to the disturbance the more fragmented it becomes, with future and past events occurring in the same space at once or out of order.
To my knowledge the only way to fix a broken timeline like that is to reinforce the strongest natural events until they force forward through your event until they override it. Once your destabilization event is essentially erased things tend to simply rebuild themselves. There's so much I just don't know about the process though that I can't say for sure what you're really doing. Nor do I know what happens to the past version of you in this process. The best option you have really is to just not mess with your own timeline. Additionally if you break a timeline it's probably best you leave it broken as fixing it may cause more problems.