You will find a new button in the posting area of the forum: There is now the option to click the little green thumbs-up icon down the bottom of each message post, if you like the post. Not quite sure how it turns out; we shall have to see if and when anyone uses the option. I think when you have clicked the green hand, a message will show that you have liked that member's post, or something similar - and there will also be a permanent record to show how many 'likes' that post has received.
(Obviously, you will not be able to 'like' any of your own posts. lol - it must just be assumed that you like it if you have posted it in the first place! )