i want to create a user for winbox that can manage a hostspot server and cannot access to other hotspot server.
please help me.

It is not possible to create RouterOS user, who can manage one HotSpot and cannot other.
The following policies exist,
user group add policy=
Group policy

Policy ::= Policy[,Policy]
Policy ::= [!]Policy
Policy ::= ftp | local | password | policy | read | ...
password -- change password
web -- connect to the router via Web
winbox -- connect to the router via WinBox
ftp -- ftp to the router
local -- login to the router from console
policy -- manage user policies
read -- read router configuration
reboot -- reboot the router
sniff -- sniff traffic
ssh -- ssh to the router
telnet -- telnet to the router
test -- test network
write -- write router configuration