ALICE packs come in three sizes. They can be used with or without their component frames. If you've removed your frame or acquired the frame and pack separately, it is relatively simple to reassemble them. ALICE is an acronym for "Advanced Lightweight Individual Carrying Equipment" and describes an entire line of integrated load-bearing items.
Insert frame top into envelope at top inside of pack. Make sure the frame is snug and evenly placed.
Thread bottom of shoulder strap assemblies through bottom areas of frame structure and back through loops at ends to secure.
Thread the tops of the straps back through releases on the shoulder pads. Leave loose until assembly is complete.
Insert the bottom retaining straps on the bag through the frame and secure through hardware as pictured--in through the top of piece, out through the bottom. Pull somewhat tightly after both sides are installed, but not as tight as possible.
Push hardware on inside of the back brace through retaining rings on bottom of the frame.
Thread retaining strap through hardware on the back brace. This strap stabilizes the brace under the load.
The strap is, essentially, triple-threaded through the buckle.
Pull the strap somewhat tightly and, while still retaining stress, fold the buckle back and lock the strap into place. Test the strap and if it's not secure, rework the threading until you get it right.
Check all attachments on the pack. It is wise to load the pack with a test load and wear it around for a bit to make sure all of your contacts and attachments work correctly before you take it to the field. Make adjustments as necessary.