It sure sounds annoying that some people don’t know how to like posts on Tumblr, but there’s always a first time for everything and you might not see the like button at first sight.
How Do You Like Posts on Tumblr?.
First of all, make sure you are signed in to your Tumblr account. Second, if you are following someone, you can also like their posts from your own dashboard yoursite.tumblr.com/dashboard . The like button is usually a heart. Third, if you want to like an article, photo or whatever post type it is, you need to be situated in the post itself most of the time, since like buttons are not installed in most themes to be shown in the homepage. Each time you are located in a particular post, and you are signed in, you will see in the top right of your screen the heart shaped button to like the post.