You are talking about two issues :

(1) Amending garden soil;
For this one, probably you need to add a lot of compost/organic matter. Before you do that, now is the best time to get a soil test:

(2) Potting Soil: Even the best garden soil will become compacted in containers. That is why, SOIL LESS potting mix is used in container. Most of these potting mixes are peat/coir/ bark fine based with some perlite and vermiculait
and fertilizer.

TO LEARN MORE: I suggest that you go to "Container Gardening" and "Soli and Compost .." forums here at GW and learn more about them. You cannot learn everything overnite ; You have to READ, Study and get into discussions. It will take some time.

Seysonn is right. Typically, garden soil is fine, if used in a garden. It is never a good idea to be used in containers. Your peppers will probably be quite happy this summer out side in the soil that you currently have. But adding some amendments to the garden could be beneficial as well. Using plain garden soil in containers is a common mistake.
Bruce

If your going to plant in the ground contact your local farm extension. For a nominal fee they will test your soil $!5 here.
They will give you a small cloth bag to send out to be tested.
Fill it with soil and once sent in they will send back the results and suggestions of what needs to be done to adjust it to whatever crop your growing. Good thing for anyone to do. Even professionals do this. Worth $15, no guess work and educational too.

Never use soil out of your garden for container gardening. Big no no

MorugaMan is right fact don't even bring it in your house any number of pests can be introduced into your plants. It helps to keep your grow aria as clean as you can. Who knows whats living in the soil outside