You are expressing a desire to do something.
Here are some examples:
“I wish I could sing better.”
“I wish I could settle the argument.”
“I wish I could sail around the world.”
“I wish I could remain calm during all of this.”
“I wish I could remember his name.”
“I wish I could replace my old car with a new one.”
“I wish I could play outside.”
“I wish I could go to the game with you.”
“I wish I could write better.”
“I wish I could own my own business.“