Look on the left side of the posts where you see the persons name.

Click on that persons name

Scroll down and you will see three options

Click on - ignore this user

To stop ignoring posts by that person just do the process again and you will see that ignonor this user now says - stop ignoring this user. Click on that.

When you have that person on ignore you will not see any content of the post they made and you will not be able to recieve any om's by that person.