We form the Present Perfect with
have/has + the past participle form of the verb (the 3rd form of the verb).
S + have/has + V3    
S - subject: I, we, you, they, he, she, it, Mary, John ...
V3 - the Past Participle of the verb (the verb in the third form): written, eaten, worked, ...
have travelled a lot. 
She has lost her pen.
The regular past participles end in -ed. (How to add -ed correctly)
work - worked
listen - listened
finish - finished
The irregular past participles are in the table: Irregular Verbs
write - written
see - seen
lose - lost