After that use your control panel file manager or your FTP client to edit the file /game_here/addons/sourcemod/configs/admins_simple.ini
For Counter Strike Source you will find it in /cstrike/addons/sourcemod/configs/admins_simple.ini
Scroll down to the end of the file and add a line per admin based on that model:
"STEAM_0:1:12345678" "99:z"
Replace STEAM_0:1:12345678 by your own steam id.
You can add multiple admins this way, example:
"STEAM_0:1:12345678" "99:z""STEAM_0:1:87654321" "99:z"
Save changes and restart your server.
Join your server and type "sm_admin" in console (without the quotes). You should see the admin menu.
