Unable to change default key in Gpg4win

I’ve recently installed a new client of Gpg4win after my last PC died.
I have imported my old public key that I used to encrypt my private text files.
I cannot workout how to set my old key as default so I can decryptt my files.
Any help would be greatly appreciated!

Hey Craig,

Do you have imported your private key as well?

Best wishes,

Yes, I’ve imported the key. So I can see it in my key chain. Though I have no way of making it the default key?