It is strongly advisable to use pass-phrase for your key pair, make sure it is a strong one and not easy to guess.
Generate a revocation certificate for your key and insure that it is saved securely.
By going to Tools-> Enigmail->Key Management, you can upload your public keys to key servers to allow receivers find it.
Write your email. Enable email encryption if you did not enable it by default from Enigmail dropdown menu.
In case if you do not want to upload your public key to a key server or the receiver has no access to the key server. You can attach your public key to the email.
Once send is pressed, the email will be encrypted and sent 😀