All sources you find go into your FamilyTree Source Box by just dropping down MY SOURCE BOX, as depicted below and adding it to the source box, your holding place for all sources you attach. From there you go to the person, click go to the source box, and you attach the person to the document. It's real simple.
The second way to put a source into the tree, and attach it to a person is to find a source that has its own unique URL. Find A Grave is an example of that, each memorial has it's own URL. Photos in Flickr, documents published in sites such as slideshare.net, and articles of documents on a blog have unique web addresses, or URL's. See photo below for an example.The URL here is long, that's OK.
The 3rd way is to have a document in hand or on a computer. I haven't seen, just heard rumors about the official word on uploading these to the tree. Ron Tanner, project manager told an audience I was in to just start scanning your documents. What I think will happen is that we will be provided a way to upload a document in to FamilySearch, then one button it into the source box. In the meantime I am using slideshare to upload documents or stories, Photobucket to upload photos, and my blog, this blog and my research blogs, to post the document with comments for a URL to attach.
I already have over 100 sources attached to my families in Family Tree.
It is an exercise of love, but it can be sort of exhausting to spend hours doing it.
Please feel free to leave a comment that is a question. We have new missionaries to train this week so it might take me a day or two to respond. I had one comment that this seems exciting. He's right, it is.