I do not think you need to add anyone to the sysadmin Role for this. Per the article you just need to add the service account you decide to use to start the SQL Agent service to the SQL Server Agent local group. On my machine that group is named...

SQLServerSQLAgentUser$MYCOMPUTERNAME$SQL2008R2DEV

...where MYCOMPUTERNAME is my computer name and SQL2008R2DEV is my instance name.