Buy a DC input. This is enough to power DC appliances, and there are many commercially available, like fans, one-pint water boilers, lights, hair dryers, baby bottle warmers, and vacuum cleaners. Many cassette players, answering machines, and other electrical appliances are DC already and with the right cable will run straight off the box. But if you want to run AC appliances, you will have to invest in an inverter. This will convert the stored DC power in the battery into AC power for most of your household appliances.
More powerful inverters are available by mail.
Use a drill to attach the meter and DC input to the top of the box. Use insulated wire to attach the meter to the wingnut terminals on the battery. Only handle one wire at a time. Connect the DC inlet to the battery in the same way. Connect the solar panel to the battery in the same way.