Customer import:
system -> import/export -> dataflow -profiles -> Customer Import

minimal details for import are:
"website","email","group","firstname","lastname","password_hash"
"base","mam@alenedam.com","General","Firstname","Lastname","6e581d6696df85c8b51c4a3d5b21d0b4:"

RE password_hash:… MD5
if you got CSV with reall passwords, the real password must be hased using MD5. Don’t forget add : at the end of the string.
real password : 123456 …. hashed password : e10adc3949ba59abbe56e057f20f883e ….. hashed password for import: e10adc3949ba59abbe56e057f20f883e: