If you are using a client-controlled vault on Unchained, you can simply add your extended public keys (or XPUBs).
Unchained has a guide on how to download your multisig wallet configuration file in their Knowledge Base here that shows where you can find your extended public keys. You can copy the text that begins with xpub to Ledgible to add each of your keys.
On the Wallets tab, select Add Wallet Data and then select the HD Wallet / XPUB option. For the HD wallet type, select Multisig and enter the number of signatures required (m) out of total keys (n) (in the format m of n). Below this field, add each XPUB as a key to allow Ledgible read-only access to look up and import your transactions on the public bitcoin blockchain.