The "Activities" drop down at the top of the screen has sections for [sM] Operations, veteran and master Flashpoints, and Uprisings. The Operations usually take a long time to 'pop' and are more often done by just joining a group on Fleet.
Guilds vary a lot. Some have strict requirements, some are very lax, etc. The Guild I'm currently in has no pressure to do anything, but often does Ops.