All plants require hardening off if grown inside or in a greenhouse. If they've never been exposed to ultraviolet light they will wilt.

As for planting out--plant outside when danger of frost is gone.
Oregano is slow growing and a perennial, so you are probably not going to get much off of it this year, but it will keep you well supplied other years, because it grows like a weed.
Parsley is a biennial. That means it grows a plant the first year--the second year it flowers, sets seeds and dies. You will get parsley this year. It will winter over and next year it will send up flower stalks that look like dill. It will drop it's seeds in the fall. If you don't want the seed heads then treat it like an annual.
Basil is an annual and very suseptible to frost. You will have to plant it every year. It is very fast growing and slugs and earwigs love it. You are best to purne it early --when it is about a foot tall cut the leader branch and then keep the rest pruned too, this will help it bush out and get the leaves before the bugs do. The leaves can be cut up and air dried in the house or you can use them fresh or make pesto with them. You can freeze pesto. The basil turns a little black when frozen but it tastes good and is just as good as fresh

I hope this helps

You probably know this, but Parsley is said to go to hell and back 3 times before it germinates.

Parsley sends out a long taproot as it grows. If you're going to start it indoors, make sure you have a very deep container. You can also wait until spring and sow the parsley seeds directly in the garden. If you do it this way, it helps to speed up germination if you soak the seeds overnight before planting.

Make sure you transplant them out of the peat pellets as soon as they are ready (when seedling is about 2 inches tall), as peat pellets are great for seed starting (I use the Jiffy greenhouses myself), but not a good seedling growing medium at all. Obviously, take the mesh off the outside of the pellet before transplanting/potting up.

Here is a link that might be useful: Steve's Garden

Basil grows easily from cuttings and is great on homemade pizza. :-) Parsley takes 2-3 weeks to germinate. I grow thyme also. It stays green in the winter here and is a great addition to chicken soup.

I sow basil and parsley direct into the garden. Parsley often self sows but not the basil. I never managed to save these tiny seeds either.

For most perennial herbs I would rather by a plant. How much do you spend meanwhile on herbs? Buy a plant and you can harvest in the same year, take some cuttings too.