more information about PGP encryption

If you install PGP command line version and also if you had .pgp file and it's key in a .asc file.

then you can decrypt the file using the following command.

pgp --import key.asc

pgp --decrypt file.pgp

for the GPG command line it's in the following way.
gpg --import key.asc

gpg --decrypt file.pgp


How Confidentiality generate from PGP encryption

Here message or file is encrypted using a symmetric encryption algorithm, which requires a symmetric key. Each symmetric key is used only once and is also called a session key. The session key is protected by encrypting it with the receiver's public key thus ensuring that only the receiver can decrypt the session key. The encrypted message along with the encrypted session key is sent to the recipient.