When you start up the client, click "options" near the "login" button. Click "use development builds" and tekkit SHOULD reccomend an update when you login. If it doesn't, re-start the launcher, go to options, click "choose manual build" and click on the top option, which will be the latest build. If that doesn't work, delete and re-download the technic launcher, re-install it, and then the first time you launch it choose the "manual build" option and choose the latest