They make weights that clip on spokes, or use the stick on weights that are used for alloy car rims. You can buy them, or find a cool tire shop and ask the tire guy if he'll flow you a strip. They break off in sections for whatever size you need.
I've also seen motorcycle wheel balancers at harbor freight.
Always stick weights to the rim. And spoke weights nearest to the rim. Don't want them to fly off.
Once you get your wheel static balanced so it never stops in the same place while free spinning, you might have to Krazy glue the weight on, because the stick on weights don't usually conform to a skinny moped wheel and dirt and oil will get to the double sided tape and they'll fly off.
Also, if your tire slips on the rim, or you skid a flat spot in your tire, hit a curb and damage your rim, and just normal tire wear will throw the balance off.
If you want to get really serious, and you have mag wheels, spin the wheel without the tire and find the heavy spot. You'll need really good bearings and no drag on the brakes.
Hopefully you have a good rim, and it doesn't have a big heavy lump in it. If it does have a big heavy spot, put the tire on and forget what I'm about to type next.
After you've found the slight heavy spot, file or grind away the inner section of the rim (where the tube would sit) until the rim is balanced. Obviously make sure there's enough metal left so the wheel isn't compromised.
On a well made rim, you shouldn't need to grind a lot, like less than an ounce. Do a little at a time, check it, grind some more.
Now you have your perfectly balanced race-ready wheel.
Mount the tire and tube,( unless it's tubeless.)
Now, since you don't have access to a machine that will spin your wheel under load (like a Dyno or a tire shaver) ride the bike for a day or so to fully seat the tire, dry up excess lube, etc.
Then balance the tire to the rim.
Usually it'll be heaviest at the valve stem. Because the valve stem adds weight, and the tube is reinforced there. If you have high quality tire, there might be a little circle, triangle,or a yellow dot painted on the sidewall. That's where the factory marks the lightest spot on the tire and you line it up with your valve stem.
Sometimes the factory is wrong.
But anyway... if you have a pronounced heavy spot thats not at the valve, mark that spot, spin the tire so that spot is opposite the valve stem, and see if it's any better.
You can keep messing with the tire position on the rim till you find the best spot, then balance it with (hopefully) a minimum amount of weight.
Congratulations, you just spent days balancing your moped wheel.
Now go out and hit a curb or do a big skid and ruin all your hard work.