Summary tab isn't showing up. What shall I do?

The shuffle doesn't have a Summary tab, it has a Settings tab and a Contents tab. If you want to add content manually just connect it to your computer and drag songs from your iTunes library to the shuffle: Syncing Music to iPod shuffle

The Shuffle uses slightly simpler versions of the "sync music" or "manually manage" settings that the other iPods use. With the shuffle you can choose to "autofill" the Shuffle from a playlist or library or drag and drop playlists or individual songs onto the Shuffle. You can also have mixture of manually added songs and automatically added songs by unchecking the box "Replace all items when autofilling" in the Contents tab: The New User's Guide to iPod shuffle

*Nothing happens.I just want the summary tab to come up so I can choose manualy sync songs.*

There is no Summary tab for a iPod shuffle. You can want it as much as you like, it doesn't exist. Also the iPod shuffle is only designed to be used with one iTunes library. You can't fill it either manually or by autofilling from more than one library/computer. To get it to work on your computer you'll have to erase whatever you got from the other computer and fill it with your own songs.