I do these all the time. Start to finish, it’s nearly always less than an hour’s work, counting back and forth between us for me to get the login & password information that is needed the first time. Renewals take a few minutes.
This certificate allows your site to be accessed via HTTPS (the “S” is for secure). It will make warnings by search entities like Google go away.
I also handle the changes that are needed to force your site to always be HTTPS.