If your friends told you that there is girl that likes you and you like her too how do you react with her and how do you tell her you like her?

Get her phone number, email or whatever and give her a call on your own. See if she would like to join you in a school activity (go see a football game?), a group picnic or something else for a specific day and time. For the first time, keep the activity to a few hours and be a gentleman.