I found the solution here
http://forum.mikrotik.com/viewtopic.php ... ss#p488479
thank you
/tool user-manager user set user1 add-credit= Qemah3_3day
/tool user-manager user set user2 add-credit= Qemah3_3day
/tool user-manager user set user3 add-credit= Qemah3_3day
[host@SS] > /tool user-manager user add add-credit=Qemah3_3day name=user1
subscriber: host
failure: such username already exists
[host@SS] >
/tool user-manager user add add-credit=3d name=user2