PSU - Homebase CB - Meter - Antenna
I would get it all set up and tuned before considering using any kind of amp.
Make sure its all running correctly in its simplest form.
Regards the PSU that will depend on how many Amps your radio is going to pull.
You will need to see what the front and rear ports on the PSU are rated at but generally the rear of the PSU will be higher rated (but not all) and most probably what you will need, almost certainly if you intend to use an amp once set up, my PSU cig socket is rated at 10 amps for example.
Details of your PSU (model no etc) will help members advise you.
CBs are generally requiring around 3 - 5 amps on legal power, adding an amp will raise it much higher dependant on how many watts its pushing.
Get the basic setup running correctly first