If you clicked the "Install button" you probably screwed up your tekkit insallation..
Just make sure your server settings is set to "CraftBukkit"
Delete all your files/folders and then unzip all of the Tekkit server files into your servers directory. Rename Tekkit.jar to crafbukkit.jar and it should work.
If you are still having issues after this I'd suggest contacting McMyAdmin because this is the only thing you need to do to get McMyAdmin to be compatible with Tekkit... everything else is standard.