What olik-olik wrote is correct, but not complete. Her first example works only with certain verbs.
I wish I had a million dollars.
I wish I were teaching English again.
I wish I could fly. (could + infinitive)
I wish I knew the answer to your question.
These examples of the present describe situations rather than actions. It doesn �t work with actions:
X I wish the police found the suspect quickly.
X I wish I finished the assignment.
X I wish you told me about that.
I hope this helps, without confusing the matter.
Bruce