You don't need it at all. SH2's original server provider Gamespy was shut down years ago and GameRanger took over. See this article for details, but I can provide a short summary too:
- Gameranger is basically a big lobby that sets up multiplayer games. You need to download a client and register.
- You only need to set up a room and invite your friends, don't open the game at all. When you press Start from GameRanger, the client opens and creates a multiplayer room within SH2. You must wait for the host to load SH2 multiplayer and then you join as well.
- Continue playing as usual :) When you quit the game, you remain in the lobby so you can start new games.