I assume you have Tekkit installed here
1. Start Tekkit (duh )
2. Go to Multiplayer
3. Click "add server"
4. In the Server name field type whatever you want to name the server (May I suggest Technicraft );
In the server address field, copy/paste this: "178.239.170.165:25573"
5. Click Done.
6. Double click the server in the list, and connect
Cya soon.