Best way to delete old Time Machine backups

I have several backups from a year or two ago for my Macs, an iMac and a MacbookPro. One old post I saw the users recommended to go into Finder, chose the Time Machine drive (in my case a LaCie), then select the device and finally select the individual backups. One other way I can see is to reformat the Time Machine drive? If viable, what's best way to do that then I can do a fresh, full Time Machine backup