First to install this mod for cs 1.6 you need to have amxmodx installed on you server.
First download the latest version of the mod and unzipp it anywhere and you will have folder which will be named Addons copy it into YourServerDirectory/cstrike then if the server is started restart it and your done!
Here are some commands for the admins:
csdm_enable - starts the deathmatch mode
csdm_disable -stops the mode
csdm_reload - reloads the mode's configurations
csdm_menu - show the menu on screen
edit_spawns - opens the respawn menu to add and erase spaws (on the newer maps you have to add spaws, otherwise all the "coming back to life" will occur in the base and not on the entire surface of the map)
And one for the players:
Guns, /guns, menu, enablemenu, enable_menu - if you give one of these commands the weapon menu reappears.