The four jacks are two separate inputs for stereo (4 ohms each side), one input for mono (8 ohms), and one output for daisy-chaining from the mono input.
If you just want to run it as a single cab with all four speakers, connect to the 8-ohm mono input. (From the 8-ohm jack on the amp, if you're only running one cab.)
If you're running two such cabs, you can either:
Connect each cab from one 4-ohm jack on the amp (since the total load with two 8-ohm cabs is 4 ohms) to the 8-ohm mono input on the cab;
or:
Connect one 4-ohm jack on the amp to the 8-ohm mono input on the first cab, and daisy-chain from the first cab output to the second cab 8-ohm mono input.
Either way will work fine but the first is preferable because it's more reliable - in the second scheme, if the first cable fails or comes loose, the amp has no load, whereas in the first scheme both cabs are separately connected directly to the amp, and it would need a failure in *both* cables at the same time to do that. Only use the second scheme if you don't have a cable long enough to reach from the amp to the lower cab in a stack.