First of all, you need to choose a speaker system that is suitable for your motorcycle. Don’t forget to think about the weather in your area when choosing them, and also how you are going to store your motorcycle. This could have an influence on how you mount the speakers.
The first step is to get the speakers out of their package and, following the instructions provided by the manufacturer, bolt them onto the handlebars. Some speakers are to be strapped there, so, depending on the model, act accordingly, following instructions. Don’t worry about bolts and nuts, as these should be provided by the manufacturer in the package.
After you’re done with placing them, you need to connect them electrically. From the battery, which is usually placed under the seat, run some standard audio power wirings (which should also come with the speakers), and connect the speakers and battery using them. Try to conceal the wires under the tank or under other pieces, as to keep them away from your legs or anything that could break them.
If the end of the cables don’t have a “clicking” system that simply allows you to connect them to the speakers easily, you will need to solder them with care, and then secure them, so the soldering work doesn’t break.
It’s best if the speakers are placed against some kind of surface, as this will give them stability and a good quality sound, as long as they’re not hitting the surface they should be stuck to.