How do I find the probability of an event?

You first have to see how many possible outcomes there are. For example, if you have to find the probability of flipping 2 coins and both of them being tails, you have to find the amount of outcomes. Here are the possible outcomes:

H,T
H,H
T,T
T,H

so the answer to the example is 1/4. If you wanna find the probability of something, you have to find the number of possible outcomes, under the amount of outcomes that you want to find the probability of.