Overwrite existing one
Simplest way to manually upgrade your e4seo component is to unblock new zip (as with original installation), exit all Excel instances and unpack new zip to already used folder for installation. After overwrite of existing files, upgrade is complete.
If you're unsure on location of existing installation it can be checked via Office (or File) -> Options -> Add-Ins dialog.
In case that you would like to change location of existing installation, manual uninstall and then install from new location is necessary.