The strings are installed with the low D string at the rear (side toward the performer) and the A string is on the outside. Both strings are wound across the top. The following picture shows the D string on the left and the A string on the right.
The strings should be wrapped around the tuner so that they are close to parallel and put the most tension on the qianjin string. This usually means that the top string needs to be wrapped very close to the end of the tuner, and the lower string is wrapped a little less close to the edge.
This particular Erhu is set up with some violin fine tuners. These are cheaply available at most music stores and can be helpful for getting the instrument into exact tune, especially if the tuners are a bit sticky.