There's a few ways to do this, and this might be a bit much for someone who's just learning XBMC for the first time, but in my opinion the best way to do this is to use the Pseudo TV Live add-on:
http://forum.xbmc.org/showthread.php?tid=169032
Crash corse:
download the zip file and using "install from zip" (see
Add-on manager (wiki)):
https://github.com/Lunatixz/script.pseud...master.zip
Once installed, find Pseudo TV under "Programs" on the main menu. It will do some auto first-time-run stuff, where it builds a fake TV guide based on your local video library. Press enter/select to bring up this TV guide.
The defaults seem to only do "broadcast channels" and then genres just for movie channels, but you can set up genre channels for TV shows as well:
Select the Pseudo TV add-on, but don't open it. Press "c" to bring up the context menu and select "Add-on settings", and under "General" select "Open channel configuration". Select a channel and change the "channel type" using the arrow keys. This will allow you to make a channel into a TV genre channel, and for a specific genre.
Otherwise I would just suggest checking out the wiki pages for
smart playlists (wiki). However, Pseudo TV is really freaking cool, so even if you're new, I'd still check it out.