How do I use the perfect tense in French?

The perfect tense in French has two parts. The first is the auxillary or first verb, which you will probably be familiar with, which takes the form of avoir (to have) or être (to be). You change this first verb depending on the person, e.g. I have- j'ai.After this, you simply add on the past participle, which is the same regardless of the subject or person with an 'e' added for the feminine genfer, e.g. j'ai mangé, il a mangé.For agreement with the plural it gets slightly more complicated, but this can be explained once you are confident with the part participle itself.