READ THE BEGINNER'S GUIDE and READ THE MANUAL. The SEQ is a complex device, with a huge number of features. You'll probably have to go over the documentation a few times before you start to really understand it. Read through the other documentation on http://www.uCapps.de as well - there's a lot of information there that will help you understand how all the devices, software, and modules in the MIDIbox universe work, and how they fit together. These articles will be more helpful to you if you've already read over the documentation on uCapps.de.
In particular, the Frontpanel section of the User Manual briefly describes what each button does, and the Menu Pages section describes how to use each menu page on your SEQ. The Sessions section gives an overview of how Sessions work on the SEQ. TK has also put together some great Tutorials with audio examples.