Based on windows 7 or 8 as a starting point. 

Backup of current data if possible. 

Erase and clean install windows 10 current version. 

Restore data to relevant locations. 

Reinstall required programs - ensuring compatibility to windows 10 . 

NB - if programs like word and excel are older than 2016 , we would direct you to purchase a more recent version from us as part of the upgrade.