The radio requires 13.8 volts DC (+/- 15%). The wall outlets in your house supply 120 volt AC (if you are in North America). If you connect your radio to a wall outlet, at best, the fuse in the power cable will pop, at worst, something expensive inside the radio will pop.
You need a power supply which converts the 120 VAC from the wall outlet to nominal 12 VDC for the radio. Astron and Samlex are good brands. The power supply will need to supply 12-15 amps continuously in order to transmit with the radio at full power.
Or, you can power the radio from a car or marine battery. Be aware that automotive batteries produce hydrogen gas, which is explosive, so they should not be used in a closed space. If you use a battery, the power cable to the radio must have an inline fuse to protect you, and the radio, from the large amount of current that the battery can deliver.