Metamask Query. Can anyone assist?

Dear all,

I have two Metamask accounts. One of these account holds the majority of my funds and is connected to my ledger.
The second account is a stand alone account (protected only by my password). This second account has suddenly grown in value and now I want to connect this account to to my ledger too.

Can anyone pls explain explain the procedure for exporting an existing Metamask account into my Ledger.

I tried to export the private key but I received a notification that I was duplicating the account?! I’m confused.

TIA

S.