boxcryptor[.]com/en/for-individuals/
techradar[.]com/reviews/boxcryptor-encryption-tool
Boxcryptor adds a driver so you'll see another drive [letter X:] in File Explorer. It automatically connects to your cloud storage, e.g. OneDrive or Dropbox, or you can set it to connect to local storage instead. You create a new folder that's automatically synced with your cloud account, & everything added is encrypted on-the-fly, or decrypted on-the-fly when opened/edited. There's decent help documentation linked at the bottom of the page that'll hopefully answer most questions.