upgrading from Yosemite to High Sierra
How can I upgrade form Yosemite to High Sierra on 2015 MacBookPro?
MacBook Pro 15", macOS 10.14
Question marked as
Click on this link and go to Section 4, How to upgrade to macOS High Sierra - Apple Support
Before upgrading make a full back up of your Mac.
Check that third party apps you use have updates available for the new OS.
Check that your printers/ scanners etc have updated drivers and software available for the new OS.