Duplicate Addresses and Repositories can be auto-merged by selecting Tools > Merge all duplicate addresses from the menu. Confirm pop-up "AutoMerge Duplicates?" by clicking OK.

Review the contact records
Make a backup before merging. Similar names do not establish that two repositories are the same institution or location. Compare contact information and notes, especially for branches of an archive or library.
After automatic merging, inspect the remaining entries and their links. The merge command handles duplicates; it does not update obsolete postal addresses or determine which contact details are current.