As for documenting hours (observation or work), OTCAS does not automatically send out email forms to your sites, like they do for letters of rec. So unless they change this for next year, you have to document this yourself - but you can get a jump on that now.
What I did was make up a letter in Microsoft Word for each place I had observed or worked and emailed it to them. It basically sounded like it came from them - i.e. "Greg T... observed here for XXX hours between (such and such dates)", and had the supervisor's name and title, so all they had to do was sign their names at the bottom. Then I had them scan and send it back to me. In OTCAS, when it opens, under the Observations section (or whatever they call it) you would create an entry for each place and attach the corresponding .pdf.