I think that i found it, im going to explain for other with the same doubt
In the archive amxx.cfg into configs folder, you have to find this:
Code:
// Default value: "_pw"
amx_password_field "_pw"
So then you change "_pw" for anything that you want
If you change it for "clan" for example, will look like this:
Code:
// Default value: "_pw"
amx_password_field "_clan"
And the administrator of the server will have to type:
setinfo "_clan" "password"
Am i right? Thanks for the help ;D