Save "aim_iceworld.bsp" file to your "Counter-Strike Global Offensive" maps folder and run it as follows:

-Extract "aim_iceworld.bsp" and "aim_iceworld.nav" to: ...Steam\steamapps\common\Counter-Strike Global Offensive\csgo\maps

-Open In-game (e.g.type "map aim_iceworld" on your dev console)

-Buy a weapon

-Action!