How do you teach the present perfect?
There are two parts to the present perfect tense - the present, and the perfect.
The present tense refers to "now" - and uses the present tense of "have"
The perfect tense refers to "happened in the past but is affecting the present" - and uses the past participle of the "action verb".
Let's look at it in a conversation:
Person 1 - "Wow - you know so much about the world"
Person 2 - "I have travelled"
So Person 2 wants to say something about having traveled the world. In stead of saying something like "I trekked in the Nepalese mountains and swam the Amazon last year" - which could derail the current conversation, Person 2 can simply make a reference to travel that has been done in the past and it's effect on the present - i.e. travel has made Person 2 knowledgable about the world.