I need to export an existing PGP key and import it into GnuPG on a different machine.
This is how I did the export:
pgp -kx myuser _myuser_public  
pgp -kx myuser _myuser_private secring.skr
(this is from the pgp installation directory that contains secring.skr).

This produced two files:

Then I moved them to the target machine and did this:
gpg --import _myuser_public.pgp
gpg --import _myuser_private.pgp
The later gives me the message "key not changed". Not sure what it means.

Now if I try to encrypt the file "test" with gpg:

gpg --encrypt -r myuser test
I get this message:
There is no assurance this key belongs to the named user.
(then there is a command prompt for Y/N).

My understanding is that I am supposed to sign the key for my user. So, I tried doing this:
pg --edit-key myuser
pub  xxxx  created: xxxx expires: xxxx       usage: xxxx
                     trust: unknown       validity: unknown
sub  xxx  created: xxxx  xxxx: never       usage:xxxx
Then I see a GPG command prompt and issue the command "sign". I get the message:
gpg: no default secret key: No secret key
At this point, I am not sure how to proceed. What else do I need to do to make the key trusted? I've read a lot of documentation on the web, but it hasn't been very helpflul.

Thanks in advance.