Hello Billy,
I'm sorry you have this problem. and I'm sorry to be the bearer of what is likely to be bad news.
I think the point Gagakev was making is that because the wall board is vinyl covered, by the time you see damp, as displayed in the picture, it is usual for a lot of internal wall damage to already have occurred. It is also quite usual that the visible dampness does not necessarily show where the source of the damp is.
You cannot cure damp by simply drying out, you need to find the source and cure it there to prevent it getting any worse. You invariably need to expose the internal wall structure to establish both the real source and the extent of the damp.
Typically you can get wet rot and dry rot arising from this sort of problem, and you must remove all affected timber as any that left may seed another infestation.
Others on the forum have carried out damp repairs, but generally its affected much more than they first imagined, and consequently it is likely to take longer and cost more.
I hope I'm wrong and it is a simple matter for you, but I do have reservations.
Good luck