OK so as per the previous discussion here about voter turnout, this month is the same as last month.
1. You can vote for two;
2. You can only vote if you have posted in this thread. The idea behind that is that it will forcibly bump the thread in the "new posts" view which is where most folks seem to view the forum from. You don't need to have entered the competition.
Say who you voted for, or why you like a photo. Equally don't say anything if you don't want to. If you don't want to post any text, just post an emoticon. Once you've posted, the voting options will be available to you.