Whether it's a single field linked through the select from other sheet field type, or a linked field via the link & load that links data from another sheet, the methods below can be used to enter data into linked fields:
You can type directly into a linked field, which will automatically display related records.
Using the link & load pop-up:
Click on the empty linked field value to bring up a pop-up displaying the listing page of your linked sheet.
You can use the full-text search bar on the top to show related results,
or filter individual fields with the arrows next to the field headers.