Ahah, good question my friends.
You have a document in your file and want it attached to the tree.
I am going to share with you 3 different ways to attach a document you have in your possesion to the Tree.
1- Wait until later. In a few months we expect that you will be able to scan a document to your desktop and then upload it to http://familysearch.org/ That is the easiest way. But there will be those of you who are like me, impatient. I now introduce you to two sites for impatient folks.
2- The first is http://photobucket.com/ Photobucket is one of those photo sharing sites. It has been around for a long time. I use photobucket for one pagers. It's free for your use if you only have one album. That is fine with me. From your desktop upload the scanned document to photobucket. Then go to my albums. Click on the picture, find the share button, and select the direct link from a website option. Paste that link into the Tree (Create a new source). Complete the information asked for and you are done.
3- Is similar to #2. It is http://slideshare.net/ Slideshare is one of the website LinkedIn recent acquistions. It works a lot like photobucket. The benefit here is that you can post multiple paged documents, like stories. It's finished posting looks a little different: click here to see how it looks, but it works great. Save it as a PDF then upload it.
PS: Some of these sites are blocked by FamilySearch, temporarily because it is possible for others to upload porn to them. Big no no, right? Someone will review your link. To have it moderated just click the get approval button and in a few days it is automatically live.