Steps to clear buffer usage in SQL server

Hello Team,

In my SQL Server production server, The SQL instance contains different databases. I have ran through the query and collected the "buffer cache used space" and "buffer cache free space" in all the databases. Some of the database buffer cache occupied more space. I just want to clear the space for those DBs. Can someone suggest what are all the steps that I need to follow to clearing used space and increase the free space?

Thanks,
Simiyon A