To learn this difficult tense you first have to learn the past participles. Regular verbs just add the ending -ed but you have to memorise the irregular ones. Here is a mind map which might help you memorise the irregular verbs first
Once you think you know the irregular verb time to practise them. Try these two wonderful games called Teacher Invaders and Half a minute.
To play the games, click on the download link, open the document in Adobe Reader and you can play. (The game will not play if you open the document in Google Chrome or a pdf reader which was not produced by Adobe).
Now that you really know the past participles you can start learning the present perfect tense. Click the link below and it will take you to a set of activities for learning the present perfect tense.
You can find free graded readers for learners of English at www.aj3000.com