Help! when should I transplant my seeds?!?!

I am on day 3 of my first grow and I can't seem to find when you should transplant to soil. I've been using the paper towel option for my germinating. On of the roots is about a fourth of an inch long. The other a bit shorter. I'm planning on transferring to red party cups with four holes in the bottom for drainage. I should plant them about a centimeter down correct? but the main question is should I do it now?
I still can't get my lame pictures to upload.

i dont know how u delete this but normally u transplant when u see roots come threw rock wool or something. or if u are doing it in like a small cup or pot then when u have about 3-4 tiers of leafs, that is also when u slowly introducing nuts. Hope i helped

Yes, you need to plant that baby asap! The longer the taproot gets, the more you risk damaging it when you plant...so when you see it peeking out, you should put it in the soil right away. Taproots are fragile, and if it gets broken, you are out of luck on getting anything to grow. Once in the soil, be sure to keep it warm and moist enough - a baggie over the top of the cup will work for a humidity dome until she sprouts through the soil. When you see green, put the lights on it and you're off and running...