To search within a particular repository or organization, 
navigate to the repository or organization page, 
type what you're looking for into the search field 
at the top of the page, and press Enter.

Taken from https://docs.github.com/en/github/searching-for-information-on-github/about-searching-on-github#:~:text=To%20search%20within%20a%20particular,the%20page%2C%20and%20press%20Enter.