Storing catalog and images on an external hard drive

I want to store my CO catalog and images on an external hard drive. Doing so will allow me to use the same hard drive on my laptop and desktop computers. I'm using CO 21 Pro. I've used LR 5.0 for the last 10 years and make one catalog a year (e.g. 2020) and keep all my shoots in order by date. Works for me... and I'd like to continue that practice with CO.  Any suggestions would need to include a detailed step-by-step process including the settings.