A search protocol is a way to document the search process.
The search protocol can also be used as a log book throughout the search and its many phases.
Add the search protocol as an appendix/supplementary literature to you article.
It is important that you document your search(es) so they in principle are reproducible and explicitly reflect your search in the various databases.
The detail in which you can register your search is dependent on the source you search in. As a minimum, the documentation must include:
By creating an account in the database or source you are searching in, you can save your searches. This means you have your search history, can retrieve updates or alerts to the search and can automatically re-run the search just before you submit your SR to ensure you have included the latest information in your article.