Opened my UPS, took the old batteries out and then put the new ones in. You just have to be careful with the wires for the front panel while closing everything back up. Put the new battery pack (two batteries) through a self-test in the UPS, and they worked properly. The originals would hardly keep my PC/monitor running for 1 minute if the power was out, so getting an affordable replacement was a must, and way less expensive than a new pure sinwave UPS. Now I can shut my machine down properly again during a power failure.