You can find the instruments by going to Project > Add Track > Instrument. In the dialogue you will find the installed instruments.
And also, you can access the mix console two other ways:
Devices > Mix Console
Right click on the toolbar > Media and MixConsole Windows > Press the “MixConsole” Button.
If you have any questions on how to use anything, you can go to Help > Documentation. There you will find all the manuals.
Also, if you speak spanish, here’s a link where you can get registered for a comprehensive Cubase LE 8 course that I wrote. It contains a full lesson on the three included instruments: Padshop, Retrologue and Halion Sonic SE.