The hosting I personally use, http://get-sourced.net can set up a Tekkit server for you if you send a support ticket, if you don't know how. Also their prices/support are awesome.
But generally, you just need FTP, and support for custom JARs. You basically upload the Tekkit server JAR and mods to the custom jars folder (if any, if not, to the main directory). This varies for every hoster though. What I see from redstonehost, you probably just submit a support ticket requesting Tekkit.