Install imagemagick, if not already present. Check it is runnable by the www-data user invoking it as convert. It is used to resize the images uploaded by the guests.
Create a MySQL db
Create the db structure running db_schema/sb_sql_schema.sql
Populate the db with the user
Copy the whole www folder in Apache web root
Copy www/config/database_example.php to www/config/database.php
Edit it according to your configuration (change at least $db_name, $username and $password)
Edit all the json files in static/. They can refer to images in the media directory using the image name only.
Replace the images in media
Place the guests pictures in user-pictures, naming them according to the picture column in the user table. If the image is missing for some users, the name initials will be shown.

Check the guests presence

Guests can answer from the mobile app to tell if they will be present at the party. You can check the list of the users that answered (or, at least, opened the app) visiting with your web browser the page report.php.

Retrieve the photos shot during the party

You'll find all them in user-pictures.