The ones that are a few inches tall are ready to go out as soon as your frost date is past - in the next two weeks, I think. The smaller ones might be OK - I would let them get a few leaf sets on them first, but I have gotten sick on some slow growers and put them out really small - the leaves faded in the summer but they came up in the fall again with the rest of the columbine, so they are hardy little things. You will notice that any volunteers you get from the wild columbine are pretty hardy and come up where they please - even in the walkway. LOL So even if they seem to fade once you put them out, they will probably make it in the long run. Do not plant them too deep or in too much sun. They like filtered or partial-day sun (morning preferred) and they like a moist, well-drained soil. Mine are in a low part of the garden, where the moisture tends to linger in the near-by surface drain I created. (I’m in SE VA.) They also do well in the outer fringes of the area where the drain line comes out for the heating/air conditioning unit - places that work for coral bells and ferns work well for columbine - use on the drier side of the bed.

Something to add to Amy’s response is harden them off before transplanting them. hardening off is important so they get used to sunlight and wind for about a week. start by setting them outside in a protected area out of direct sunlight (columbine likes shade anyhow) for half a day and each day give them more time outside by a couple of hours until they are out 24 hours. Now they are ready to plant.