Two things to note, before you go asking for help!
1) Planar Exodus always crashes the first time you start it. This is true of both server and client. Just restart it! It'll work.
2) Planar Exodus occasionally crashes upon generating a new world. This is a CodeChicken error and we cannot fix it. This will never corrupt your worlds. Again, restarting is guaranteed to fix this problem.
With that out of the way -- Use the Discord server.
If you need help with something, post in the #plex channel. Discord lets you attach files to your messages; if something crashes, nothing is more helpful than uploading the Forge log!
( You can find that in your Planar Exodus install directory. It's called