I bottle all my beer and this is what I would do.
For a lager I would use 5g/L of sugar or glucose; weigh this out into a pan or pyrex jug, add a small amount of bottled water or water that you have boiled for 15 mins, and heat gently on the stove while stirring to disolve the sugar; when disolved cover with tin foil and put in the freezer.
Then I'll go ahead and sanitise all my bottles and equipment.
Then you are ready to transfer the beer from your FV into another bucket/vessel with your siphon tube. Once you have started siphoning, add your sugar solution, which will still be warm, and complete the transfer from your FV, and on completion give a gentle stir for good luck.
I then go ahead to fill the bottles, cap and keep at room temperature for say 7 days before storing in my cellar at 15C.
A good guide for the amont of priming sugar for the beer style is John Palmers book, available on line here
http://www.howtobrew.com/section1/chapter11-4.html and hopefully this will take you to the right page, if not it is at the end of section 2. You can print off the nomogragh and use it to work out the sugar. You will have to convert to grams & litres, and also the temperature means your fermenting temperature.
Good luck :
