Express is a regular verb so the past and past participle are the same:
expressed
The past participle is had.
Done is the past participle.
The past participle of the word "Find" is the word "Found."
The past participle of the word "pick" is "picked".
The past participle of the word "finish" is "finished."
The word "invited" is the past participle of invite.
The past participle of "swear" is "sworn."
The past participle of the word 'fall' is 'fallen'.
The simple past and past participle are both welcomed.
The simple past and past participle are both hopped.
The past participle of "express" is "expressed." It is used in perfect tenses and passive voice constructions, such as "She has expressed her feelings clearly."
The word "it" does not have a past participle as it is a pronoun. It is only verbs that have a past participle.