Different seeds have different germination temperatures. If the seed package says a temperature that is for seed germination. After seedlings appear growth of fungus disease needs to be avoided by increased light, but not direct sunshine. Air circulation needs to increase and in a small greenhouse this often means a fan will be needed. A cooler temperature is also helpful to prevent fungus growth. Before your seedlings can be put outside they will need to be hardened to the outside temperatures by puting them out in a shady area for an hour at a time for a few days before leaving them out all day or all night. They also need to be protected from birds or mice that often eat tender seedlings. Al

If you are using a greenhouse kit, I would be careful of overheating once you put it outside. I do Winter Sowing, which we sorta make a primitive kind of greenhouse, a plastic covered container, and I was amazed when I put a thermometer inside the covered container. 60 degrees outside could be 80 degrees inside, and easy for your plant to fizzle.
Unless maybe your kit has ventilation to take care of that.

ellenr