If you are sharing a file with LOTS of people at one time, it may be easiest to share with them using a link that you paste into an email or on a website. Google allows you to directly share a file with a max of 200 people. However, if I need to share with more than 10, I don't necessarily want to type in all of those names, so I share with a link. When I send them the link in an email, they gain access and can then find the file again the next time they come back to their Drive > Shared with me.
Here's how to do that:
I might also want to add that link to my course in itslearning so that I share the file with my students or with other teachers. To do that, follow the same steps as above for getting the share link from the Google Apps file, then:
Is there anything that you think I've missed? Remember that this is only part 2 of 4-5 ish, but let me know what else you need in the comments below!