Well, I'll assume that you have an XC or XCT, since you posted here. You really ought to include the year and model somewhere in your signature, for instance.
If you're going to keep things simple, I would suggest that you use a wire pair that's already present in the fairing. I don't know whether this holds across all model years of the XCs and XCTs, but usually the factory harness has at least one extra wire pair for the Vic driving lights or fog lights or whatever they are. This pair -- ground and hot -- will be inside the fairing, with maybe a label on it, and terminated in a nice factory plug. You should always use a real ground, either as part of a pre-existing wire pair or a pair you add yourself; going old-school -- relying on connecting to some chuck of metal on the bike for a ground -- is asking for trouble. Maybe in the all-steel old days that trick worked, but in these days of multiple metals, and plastics, and fuss-budget ECM nanny programming, using the frame is asking for trouble (IMHO).
And the wire will be hot only with the ignition on, which is what you want (so you don't have to remember to turn off the added lights). And it will be fused high enough for your needs. If you want additional on/off control, then you have to cut the hot lead, and add wires routing it to and from an added switch. The stock dash will have one or two blank spots, typically depending on whether you heated grips or not. Those dash blanks accept Vic switches, or those found at any auto-parts store in that standard size (and if they're a tiny bit bigger than the blank cutout, a little filing will fix that).
For connecting to that wiring harness extra plug, there are some threads that list suppliers of matching plugs. Those plugs usually require that you insert pins inside the plugs, i.e., assemble them yourself. The easier way -- if not as "clean" -- is to just cut the plug off, and then deal with the two wires with solder, or Posi-Locks, or Wago Cage Clamps, or whatever connectors you're used to using.
Taking off the fairing is a 10-minute job, and presents no challenges. If you get into removing the dash, there are some screws behind the forks and some over the tank that are a pain to deal with. (The dash blanks can be removed without taking off the dash, but I think it's easier to have the dash off. If you have heated grips, those spade lugs usually fall off, and should go back in specific positions. There's also the sensor for the ambient temp reading.)
If this project is just the start of many electrical farkles, you may want to get into the realm of battery-terminal extenders or, beyond that, relays and fuse panels. Those would be the subject of another post or two.
Hope some of this is the sort of thing you're looking for. Rummage around inside the fairing, and you could be all set.