Is is possible to lock topics?, as in no one can post?

yes.
Make sure you have assigned yourself moderating permissions for that board. - Admin panel -> forum boards -> edit the board in question -> either select rank moderators or you can input the profile id of a particular individual.

Then when you are looking at the forum boards on your website you should see a "moderate" button at the top, click that and then you will have the ability to, lock, sticky, move or delete the topic. So for information topics you can lock and sticky so that its easy to find!