If you are having problems putting the rigged character to a new RESE POSE.... check out https://www.youtube.com/watch?v=iMVs6BP1Q48 an old 2.78 tutorial but works great for 2.82...
But you do have to follow each step see
https://nixart.wordpress.com/2013/03/28/modifying-the-rest-pose-in-blender/
for written instructions