Left and right interface outputs are unbalanced. Ie. pair of TS or rca cables. (Two conductors each - tip and sleeve)
Speaker input is one stereo 3.5mm jack. (Three conductors - tip, ring and sleeve)
The tip of output left needs to get to the tip of 3.5mm jack.
The tip of output right needs to get to the ring of 3.5mm jack.
The sleeve of both output jacks needs to get to the sleeve of 3.5mm jack.
Basically, you need a 3.5mm stereo male to 2 x 1/4 mono male adapter. They're pretty common.
That will get left and right un-amplified signals to your speakers.
You'll find the amplifier for both speakers is built into the right speaker, hence the "to left speaker" output.
You need to connect that to the left speaker as normal.
It is an amplified output. You can't bypass it.
Make sense?