A SQL Server technology that supports the creation, management, and delivery of both traditional, paper-oriented reports and interactive, web-based reports.
I'd suggest leaving the existing certificate in place rather than removing it first, keeping it in the certificate store gives you a quick rollback if anything goes wrong.
Before you start, just confirm the new cert is in the Local Computer Personal store with its private key, the SSRS service account has read access to that key, and the Subject or SAN covers every hostname your SSRS URLs use. Backing up the SSRS encryption key beforehand is also a good habit.
To swap, open Reporting Services Configuration Manager, go to Web Service URL then Advanced then edit the existing HTTPS Identity to point at the new certificate, and Apply. Then do the same on Web Portal URL Advanced. Test both URLs from a client machine afterward to confirm the new cert is being served.
If anything looks off, simply point the binding back at the old cert, recovery only takes a minute since it's still in the store.