Step 1: Go to the gear icon in the upper right hand corner
Step 2: Choose Admin
Step 3: Look for Users in the middle column and click the link
Step 4: Select the user to be deleted (if an active user they will appear on the screen, if the user is still pending then look to the upper right and select pending invites)
Step 5: With the user you want to delete selected click the trash can icon.
This will remove the user from the account.