Once you have mapped your Bank, you can create the Relationship between the Constituent and the Financial Institution.

You can only map to Banks/Financial Institutions that are mapped in your Template as you will have to select the Bank Mapping from the Default Value in the row for the Financial Institution.

Once imported, this Relationship will show on the Constituent’s Relationship tab as shown below.

After you have mapped your Financial Institution, you can link that Relationship to a Gift (shown below).