There are a couple of ways this can be done; adding to the bottle directly, or adding to the bottling bucket, mix, and then dispense to the bottles. I've never added it to the bottle directly so I cannot speak to that method. I keg everything now, but have bottled in the past.
I've done this a couple of times and added the priming sugar to the bottling bucket and mixed well (slowly - you don't want to add oxygen at this stage) and then off to the bottles. Worked very well.
The amount of sugar will depend primarily on batch size and the level of carbonation desired. IIRC, 3.5 or 4 oz of priming sugar for a 5-gallon batch seems about the average dose. You'll want to double-check that to be sure, though.
The sugar is put in a pan with some water and heated until it just comes to a boil, then shut off and allowed to cool with the lid on for a while (at least until it is just warm to the touch). Then it may be poured into the sanitized bottling bucket (or other vessel of your choosing - whatever you'd normally use for bottling) and the beer racked onto it and stirred gently- again; slowly so as not to introduce any oxygen.
Bottle and cap and condition at normal fermentation temperatures for 2 or 3 weeks (or whatever is recommended for the style) and chill, open and enjoy!