This can get a bit tricky, but once you get the hang of it, can be done fast enough. First, some technical notes: In order to get higher voltage, you need to connect two cells in series. This means that the negative part of the first connects to the positive part of the second. As you continue to add more cells in series, you will get a higher voltage from side to side on your solar strip. This is all good, but if your cells are small-ish, they won't generate much amperage. So even if you have a high voltage, you probably won't be able to give it any load (probably will hardly light an LED). In order to get higher amperage through the circuit, you need to connect cells in parallel (positive side to positive side, negative side to negative side). When you do this, make sure the positive and negative leads (copper mesh in this case) don't short themselves out.

I found that the best way to connect between two cells was to use hot glue and some conductive mesh. The mesh is good since it allows light to come through it, and we all love glue guns. So all you need to do is glue the mesh onto the solar cell surface. Its always better to have a longer strip of mesh on the surface, with a big enough shared surface space between the two. Always check with a multimeter that there is connectivity, and that there is voltage coming through. Its a bummer later to try and figure out where the problem is.