Hi No Sound,
Welcome to the forums.
It would be really useful of you could provide some more details about your system and exactly What you are doing to try and make some sound!
The built-in sound card in all Mac's will work fine.
Try Logic Express > Preferences > Audio
to make sure core audio is turned on and the correct device is selected.
Try the following:
1. Create a new audio Instrument track
2. Click in the I/O slot on it's channel strip and select an Instrument.
3. Press the capslock key to display the Caps Lock keyboard.
4. Press a key on your keyboard (e.g. F, G, H etc)
5. If you cannot hear any sound still, look at the Transport display to see if any MIDI info is being display when you press a key.
In Logic, it's really important to create the correct type of track...
Also, I'd really recommend you check out this tutorial, or even the demos, as it will get you up and running in no time:
Let me know if the above helps or not.