How to use GPG?

Simply we can run this:

gpg --full-gen-key

Then we will have some interactives.

Key Type

It's optional, but I oftenly use RSA and RSA (number 1)
Keysize (Bits)

It's more secure to have more bit or simply we can take the maximum bit, let's say maximum number is 4096, then we can put 4096
Expiration Time

If we want to use this key on all the time, we can set to 0 to have the never expired key.
Expiration confirmation

let say I set 0 as the expiration date which mean it will never get expired, then it will try to confirm us that we really want to create a key which never get expired.
Identity
1. Name
  
  Put your name, minimum length is 5.
2. Email
  
  You'll never get email for this, it's just for identification purposes. (optional)
3. Comment
  
  Just another information we want to put, maybe to identifying something. (optional)
Identity confirmation

It will ask you to confirm your identity, we can input O (O / Oscar character) to confirm that it's correct.
Password

Finally we can put password for the created key, we're going to need this password to decrypt encrypted file.

gpg -r <uid> -e your-whatever-file.zip

replace <uid> with your created key, then a new file with the .gpg extension will be created.

gpg -d your-whatever-file.zip.gpg

or if we want to put the unlocked data into a file, we can use

gpg -d your-whatever-file.zip.gpg > your-whatever-file.zip

gpg --list-keys

or we can just specify a <uid> to know the information of specific key

gpg --list-keys <uid>

gpg --export-secret-keys <uid> > output.key

You're going to type your password to able to export the key.

gpg --import output.key

to be able to delete the keys, we need to delete the secret key first, then deleting the key.

gpg --delete-secret-keys <uid>
gpg --delete-keys <ui>

References:

Fiko Borizqy