What I would do - and I can see many of you cringing -
Soak it for several hours in hot water-
Wash it gently in warm water -
Dry in a dryer - gently - until "just done"
See what it looks like. For me, it's easier to try to work with what the fabric "wants" to do, than trying to beat it into submission.
If necessary, trim the panel so it is "square enough" to work with.