For the standalone software, simply extract the files, and upload them into your current biblesupersearch directory.
For the WordPress plugin, use the updater within your WordPress control panel.
If you are using legacy version (Bible SuperSearch 2.2.x or older), you will need to delete the existing Bible SuperSearch and install the new version.
Bible SuperSearch 2.6.0 is a complete rebuild of the software from the ground up.
Please see our Legacy to Modern Migration Guide