If what Steve suggests doesn't work (you will sometimes encounter stubborn allbums that won't group easily), select all of the tracks on the album and do a Get Info on all of them at once.
Then make sure the Artist, Album Artist, and Album are all exactly the same.
If that still doesn't work, repeat the previous again, but change the Album to something different. It can be as simple as adding a space at the end of the Album name. That should group all tracks on the album. You can then go back into Info and change it back to the original value.