I can’t login

I just created my wordpress-account today by installing it on my computer. But when I try to login it says, that it’s the wrong password (My username is “admin” – I know). And when I ask for a new password it says that I don’t have an account. What to do??? I really hope someone can help me!!!
I don’t understand the answers that have been given to other users, who have some of the same problems, so it would be great to get an easy understandable guideline if possible…
Thank you!