Go to:Administration → Site administration → Plugins → Install plugins.
Then upload theme ZIP file space.zip. You should only be prompted to add extra details (in the Show more section) if your plugin is not automatically detected.
Check the plugin validation report
Done
Go to the Site administration → Appearance →Themes → Theme selector
Select: Space theme
Done
After all clear global cache.
Go to: Dashboard → Site administration → Development → Purge all cache
Log into your Moodle site via FTP client and go to Moodle theme directory located at your-Moodle-site/themes/.
Unzip the theme file you downloaded from ThemeForest and upload only the extracted theme folder (space.zip).
Ensure that the new theme folder and its contents are readable by the webserver.
Now login to your Moodle site and go to Administration → Site administration → Notification, you will see a Notification for theme to be installed. Click “Upgrade Moodle Database now” button to continue for the installation procedure.
Go to: Site administration → Appearance →Themes → Theme selector
Select: Space theme
Done
After all clear global cache.
Go to: Dashboard → Site administration → Development → Purge all cache