I use a bungee cord to keep it tight. Put the solar panel in the sun. It takes 5-8 hours to charge a dead battery; 1-3 hours to top off a weak one. It will run radios, fans, and small wattage lights all night, or give you about 5 hours of continuous use at 115 volt AC, or about an hour boiling water. This system may be added on to with larger panels, inverters, and batteries.
That's quite a project that'll kill an idle Sunday afternoon—and power a good deal of your electrical equipment. And save you a bunch of money. Happy solar building.
For more info on specifics, and how best to operate the system, head over to Rain.org.