Jamie,
you are going to want to hold off on the priming sugar until the moment you are ready to bottle.
Racking to the secondary isnt always necessary unless you want to use it to dry hop or to get a little extra sediment to fall out of your brew.
if you introduce your priming sugar right now you are going to jumpstart fermentation again and dry out the beer a little and then have to add more to get carbonation in the bottles.
just rack into the secondary into a smaller vessel, you want little to no headspace in your secondary fermenter because CO2 production has slowed and you run the risk of bacteria filling the headspace. make sure everything is sanitized properly and rack over. after some sediment has fallen out and you have hit your FG, rack to a bottling bucket while adding your priming sugar, then bottle as normal.
The priming sugar is to allow a little bit of yeast to ferment in the bottles to build up CO2 which will give you the carbonation in the bottle. Because the excess CO2 has nowhere to go (say..out an airlock like in your fermenter) it cannot push the glass and cap (unless waaay to carbonated..look up the term bottle bomb) and forces itself back into the beer where it is absorbed over time