$ gpg --import ~/keys/pub/tom.asc
You can change the trust level of a private/public key very easily using the following.
$ gpg --edit-key <Key_ID> trust
At the prompt select a number between 1...5 depending on your level of trust of the key.
GPG should automatically find the correct secret key, however one can be defined if required.
$ gpg --batch --yes --passphrase "SecretSquirrel" -o ~/outputs/encryptedFile.txt -d ~/encrypted/encryptedFile.txt.gpg