Any kind of seedling needs light, and heat. Like a heat tray underneath the seedlings for about 12 hours on and 12 hours off. Seedlings need humidity to grow, too, (most of them, as it really helps them grow quite well) and they are still a crapshoot. They need moisture, but not WETNESS, and you'll often be waiting weeks for the little guys. If you don't have a lot of sun, it is necessary that you get a grow light/lamp for them. Growing seeds isn't recommended for beginners, as it's very difficult and many things can effect the seeds. I'm a beginner myself, and I was truly looking into growing seeds... but it can be expensive and time consuming. If you're willing and ready to go, then I wish you great luck!
Look up what time of soil the seeds need, how far to push them into the soil, how much light and warmth they'll need, how quickly they grow. You'll most definitely need a grow lamp.Cryptomeria grow in forests on deep, well-drained soils subject
to warm, moist conditions, and it is fast-growing under these
conditions. It is intolerant of poor soils and cold, drier climates.