when was the charger last serviced? It kind of depends on what size pulley you are using. If it's got a 65mm one then you prob want to get it serviced or at least checked over every 20k. Less often if the pulley is bigger. If you don't know when it was last looked at then get it looked at ASAP.
To tension the belts you move the actual charger itself like tensioning a fan belt by moving the alternator on lots of other cars. Slacken off the two 19mm head bolts, slacken off the 13mm bolt on the mount that holds it to the exhaust manifold. Then you need to get a 1/2" drive bar into the square hole on the charger cover, you'll need to take the grill off to get at this properly.
Really with the standard belts you want to get them as tight as possible, I dare say there will be an actual torque setting to do them to but I don't know what it is.