Personally, I click on the tab to the right that says my blog name. Not the link to my blog, but the tab right above it, and it should say all the activity that has gone on within your tumblr.
I hope that helps!
From what I understand... it's like a blog scrapbook. You're allowed to post blogs, quotes, pictures, audio, and even audio blogs basically anything you want. It's really neat. It kinda has a twitter feel to it as you're allowed to connect your tumblr to your twitter and also you have a dashboard that allows you to see the peopel you're 'followings' recent stuff that they've posted.