Wah How to use "Wish".

1.) We can use Wish to talk about a desire connected with the present situation.
We would like things to be different from what they are, we might regret about the present situation.

Wish + Past Simple Tense

• I want to buy that car but I don't have any money. I wish I was rich. (You regret that you don't have enough money to buy it.)
• I am too short. I wish I was tall.
• I feel terrible that I can't swim. I wish I could swim.
• It is raining and I don't have an umbrella. I wish I had an umbrella.
• She wishes I could buy that guitar.
• John wishes his son would study harder.

Note: In formal English we usually use were instead of was.
    I don't know how to solve this problem. I wish I were clever.
    I am too short. I wish I were tall.

2.) We can use Wish to talk about a desire to change the past situation. (You didn't do it in the past.)

Wish + Past Perfect Tense

• I wish I had not eaten too much. (I ate too much and I feel bad right now.)
• Mary wishes he had not come to the party last night. (But he came to the party.) 
• I wish I had not bought such a useless thing. (I bought a lot of useless thing and I regret about that.)
• I am so thirsty and I don't have water. I wish I had packed water. (But I didn't pack it.)
• She wishes she had been born twenty years earlier.
• They regretted not passing the test. They wish they had passed the test.

That woman was very beautiful. I wish I had known her.