can you help me with perfect tense

Answer 1

Here is one of the best explanations of the formation of the perfect tense I've seen:

http://www.slu.edu/colleges/AS/languages/classical/latin/tchmat/grammar/whprax/w12pftns.html

Let me know if you have further questions.

Answer 2

Here is an example. You can use this pattern with other verbs:

vidi = I have seen
vidisti = you (s) have seen
vidit = he, she, it has seen

vidimus = we have seen
vidistis = you (pl) have seen
viderunt = they have seen

The present perfect is used for an action that started in the past and continues into the present. (Different from the simple past which is an action that was completed in the past.)