How do I learn about planting Hatch chiles ?

Unless you have visited New Mexico, or are a serious chile lover or foodie, not many people know about them. Not a typical seed sold by many of the seed catalogs, or if they do, available in limited quantities.

https://www.sandiaseed.com/blogs/news/how-to-grow-hatch-chile

https://www.hatch-green-chile.com/chile/

https://www.madeinnewmexico.com/products/hatch-new-mexico-chile/hatch-green-chile-seeds

Hopefully you are in the right zone to grow them.

Just plant the seeds in potting soil in small containers indoors. Cover the pots with a clear plastic hard shell, or with Saran Wrap. Place in a sunny window, but not in direct sunlight. When the seeds germinate in about a week, sprinkle water over the seedlings every day. Keep the cover off 4-5 hours a day, but cover it the rest of the day, for the second week. Then leave the cover off and let the pots get as much sunshine as puss I’ve. When the pepper plants are about 5” y’all, they are ready to be planted outside, either in larger pots or in the ground, where they can get sunlight up to eight hours a day. More sun= more capsaicin = hotter peppers. Best wishes and good hatches, Haw. ☺️

https://homeguides.sfgate.com/grow-green-chiles-23129.html

you never said where you live & that will matter the most for when to start them. Peppers of any kind can be grown anywhere as long as they get full sun. Here in Arizona we are just starting into our best growing time,the peppers are just beginning to get some size in the cooler days & hot sun,the rest of the year the sun scalds everything unless it's started in March so it's sun tolerant by April. This year it was in the 100's in March so nothing grew or had flowers to get pollinated for fruiting.Google your growing zone. I used to live in the Ohio,Indiana,Michigan area and main growing rule "never put out seedlings/starter plants til after Mother's Day" avoiding any late snow,freeze or frost that will kill them.