Step 1 - ThemeForest provides you 2 options for downloading your purchased item.
- All files & documentation - the file you need is hummingbird.zip in uploads folder.
- Installable WordPress file only - you can use the downloaded file directly in this case.
Step 2 - Navigate to Appearance > Themes.
Step 3 - Click "Add New Theme", then "Upload Theme".
Step 4 - Click "Choose File", then select hummingbird.zip which was explained in step 1.
Step 5 - Click "Install Now" and activate the theme after installing it.
Step 6 - Install the required plugins by clicking "Begin installing plugins".