Only established/premium members are able to like something. https://forums.digitalpoint.com/help/established
On the lower right side of the post, you will find a like link. There is a reply link on the right side of the like link. Click on the like link to like the post.
Until you will become a "Member" by receiving at least "3 likes", you can't see the 'like' option through your account...and so you can't like any other's post.
You will get the ''like'' button when you have 3 likes from 3 different established members of the forums. Established members on the forums are just those who have 3 or more likes. When you get those likes you will be able to post threads in B/S/T section. This is abridged version,more about this you can find in ''Rules'' which you should read it.