There are two teleporter stones in the game, which you can use to telpeport back and forth between. Lanilor gives you one the first time you enter the catacombs after freeing him, and the other you can either teleport to or find near the bottom of the catacombs.
Usually you leave one wherever you set up a base (ie a bed and chests to stash excess loot, possibly close to merchants) and keep one with you. When you want to get back to base to sleep, pick up potions, drop off loot, etc, you can drop and use the teleporter stone you have, then use the teleporter stone at the base to get back to where you left off, pick up the teleporter stone (drag and drop it into an open inventory window, or onto the menu bar interface along the bottom of the screen) and continue exploring.
If you have both teleporter stones with you, you can toss one through some locked grates or into otherwise inaccessible places, and teleport to it (drop the other stone first so you can get back, or keep it in your inventory and toss the first one again).
You do not need to do anything with the teleporter scrolls; they will automatically activate a teleporter pad if you have the associated scroll when you click on it. A teleporter pad must be active to teleport to it (there will be a blue flame on the map beside the teleporter pad if it is active). Once you activate the next teleporter pad, you will be able to click on the flame to teleport between active teleporter pads.
If you don't have the manual you can download it as a
pdf file.