A couple of good guides for setting up OctoPrint on a Raspberry Pi (using Guy Sheffer's OctoPi image).
Thomas Sanlanderer's Getting started with OctoPrint on the Raspberry Pi... guide is a good one for basic setup. Scroll down the page for both written directions and the video.
Joe Mike Terranella's OctoPrint Tutorial Series of videos I've found helpful, starting with one on basic setup, and progressing to others on more advanced topics (accessing from anywhere, web cams, plugins & slicing with Cura, touchscreens, etc.)
Both of these may be getting a bit dated, since they were made using older versions of the OctoPi image, but they still seem to work. (They will both need some minor updating when OctoPi 0.15 comes out, since it handles editing your WiFi settings a bit differently.)