Hover over Social on the left menu and click Friends

Find the friend you want to remove and click on the icon on the right side of their image

Click Yes in the text box that appears - This will remove the member from your friends list!

Tap More in the bottom toolbar and select Friends.

Tap the three lines icon to the right of the friend you wish to remove and choose Remove Friend

Additionally, you can remove a friend from within a game by tapping on their avatar and selecting Remove Friend