Rich,
- What frequencies should I load into memory slots?
That will depend on your area of interest. Your radio is FM only so this is likely to include local FM repeaters, any frequencies used by your local club for its activities (e.g. "nets") and any that are of specific interest that you therefore might end up using regularly. For example I have the ISS (145.800) programmed into mine because I sometimes like to receive SSTV images that they send out from time to time.
- If I don’t load a frequency into a memory slot, does that mean I can’t RX/TX on that frequency?
Not at all. Programming a frequency into a memory just allows you easily recall it by name or memory slot number. When programming in a repeater frequency you can also conveniently set the offset and CTCSS tone. On an analog radio you should be able to tune in to any frequency within its range and listen in but the radio will need to be in VFO mode as opposed to memory mode. The UV-5R has an orange button on the front to allow you to switch between the two modes. Once you are licensed as a radio amateur you can also Tx but be aware that your license will allow you to transmit within the amateur radio bands only. For example, your radio covers the PMR frequency range, but it is unlikely to be legal to transmit on those frequencies using this radio because it is not designed to PMR radio specifications and exceeds the max power output that is legally permitted for PMR transmissions. Don't assume that just because the radio is capable or a band is license free, that it is automatically OK to transmit on it. Details for the Rx and Tx frequency ranges the radio is capable of should be covered in the manual, but it is also worth being familiar with the bandplan and regulations governing usage in your country. Going off subject a little here perhaps but it is good to be aware.
How do I know what frequencies to use for repeaters in my area (or outside of my area)?
To find repeaters in your country/area you could have a look at https://repeaterbook.com/.
BTW, this is for a mobile Mirkit Baofeng UV-5R MK5 radio.
Its a good choice for a first transceiver and to have a general listen around.
Rich