Scissors are normally only sharpened at the beveled side, never at the flat inner side. The quickest way to ruin scissors is to grind a bevel at the inside of the legs. Depending on the purpose, scissors have either a completely smooth inner side, or an slightly corrugated one. The latter is to help the scissors grab the materials it needs to cut. This is necessary, because scissors cut with shearing force; if the material slips, the scissor fails to cut. For the same reason, as Emmanuel already pointed out, scissors are seldomly honed to a refined, polished bevel,though it depends a bit on the purpose of the scissors.
For normal household task (cutting paper, string, fabric, tape, boxes, etc) I sharpen scissors, by hand, with the same simple small round file that I also use to sharpen my chainsaw chains. It's a fine type of file, they are sold at ecery store that carries chainsaws, they come in varying diameters, but for scissors it doesn't matter much.
If you can take the scissors apart, that would be helpful, but I usually don't. Put the legs, one at a time in a vice, and refresh the bevel with a few strokes of the file. It is important to keep a constant angle, that matches the angle already present. Guiding the file with both hands this is not difficult, certainly easier than sharpening a knife. That is basically all there is to it. If you have a finer slip stone, you can refine the bevel a bit, but for the purpose described that isn't necessary. The first cut after sharpening must be made into paper. Do not close the scissors, because it carries a few burrs and will cut into itself. Cutting into paper removes these burrs without harming the new edge too much. Do not attempt to strop the bevels, nor the inside.
If the scissor is meant to cut hair, you may want to put a more refined bevel on it, not because it won't cut with my coarser bevel, nut because it will cut lighter and will cause less fatigue to the hands. For 99% of appliances, scissors are not used for prolonged times and fatigue is not an issue. In that case, a coarse bevel is will certainly suffice.
Kind regards,
Bart.