Perfective verbs only!
Remove –ть and add –в (–вшись for reflexive verbs):
• прочитать — прочитав (having read)
• открыть — открыв (having opened)
• почистить — почистив (having cleaned)
• вернуться — вернувшись (having returned)

N.B. some exceptions:
• войти — войдя (having entered)
• привести — приведя (having brought)

Meaning and usage:
Describes an action that has taken place before the action described by the main verb. Translates as: having done (negative = without having done), after doing ...
Прочитав твоё письмо, я положил его на стол и задумался.
After reading your letter I put it on the table and fell deep into thought.


I haven't understood adding –вшись for reflexive verb <- mean what???
. And can explain me what is reflexive verbs.../?? Thanx