On your FireStick home screen, select the Search icon
Type Downloader and select it from the suggestions
Download and install the Downloader app
Go to Settings
Select My Fire TV
Select Developer Options
Turn on Apps from Unknown Sources
Open Downloader
Enter the Cinema APK download URL
Download the APK file
When the download finishes, select Install
Open Cinema after installation
If prompted, allow the required permissions
Use Cinema on your FireStick