Q.When do you transfer seedlings outside?
When do you transfer your sprouting seedlings to the outside? Or do you put it in a planter first? I started some seedlings from a kit and they are sprouting, so what’s my next step?

Here is a link to a vegetable planting guide that will tell you the ideal temperatures for transplanting seedlings in your garden:
http://extension.oregonstate.edu/deschutes/sites/default/files/Horticulture/documents/soiltemps.pdf
The first step is determining if your seedlings are truly ready to be transplanted into your garden. The article below will assist you with that determination. The general rule of thumb is that when a seedling has three to four true leaves, it is large enough to plant out in the garden.
When the seedlings are ready, they need to be "hardened off". The article below will explain the hardening process. Basically, hardening is a process where you get your plants acclimated to outside temperatures before you place them in the ground.
https://www.gardeningknowhow.com/garden-how-to/seeds/how-to-harden-off-your-seedlings.htm