Some gave me the following recipe for rice krispy figures (1 packet of marshmellows, 1 tbsp margarine and 2 cups of rice krispies.) Do I just melt the marshmellows with the marg then place into a container?

What size packet of marshmallows? Two cups does not sound like enough rice cereal for even the smallest packet of marshmallows. I use the regular recipe for Rice Cereal Treats and if my RCT sculpture is going to have to last a long time I leave out the butter/margarine. The recipe is here:

http://www.ricekrispies.com/#/recipes/the-original-treats

How soon can you make it? Would it be too early to start doing it for a cake in February?

If its meant to be eaten I wouldn't start till a week or ten days out. RCT don't really go bad, but when they go stale they can taste quite nasty. Of course, if you've never done a RCT sculpture before, you might want to try a practice run or two to see where you might need more advice. In that case you could start earlier.