The second option on how to install our Theme would be the upload via FTP manager. It really doesn't matter which of the two ways you choose, just choose the one you feel more comfortable with.
1. Login to your FTP account and navigate to your WordPress Installation directory
2. Navigate to the folder /wp-content/themes/
3. Upload the "Spina" folder (not the .zip-file). This is the folder located inside the spina_package/theme/spina.zip file you've downloaded from Themeforest.
4. Now log into your WordPress backend
5. Navigate to Appearance > Themes
6. Find the Theme and click Activate
If you are experiencing any issues during the installation I would recommend to check out this Tutorial by Envato