I totally understand how to import other people's keys and how to encrypt my own messages to send to others. But I don't think I know how to post my public key. In my GPG keychain I've made keys with my address that say Sec/Pub under type. But when I export it it's some weird file that I don't know what to do with. I expected a pgp block like all the vendors have on their profiles, so they could upload my key. Am I doing something wrong?
If you're using Tails, it is indeed not obvious;
Manage keys --> select your PGP key --> edit --> copy
Edit: that 'weird' file might contain your private key, so don't share it.