Golku isn't in the Amazon or Google app stores, so the TV gets it through the free Downloader app. You type one address and it installs.
On the home screen, open Find, then Search, type Downloader and install the orange app. It's free.
Open Settings, My Fire TV, Developer options, Install unknown apps and turn Downloader on. If Developer options is missing, go to My Fire TV, About, click the device name seven times, then go back.
Open Downloader, select the address box, type golku.com/apk and select Go. When the download finishes, select Install, then Open.
Golku shows a code and a QR code. Scan it with your phone, or open golku.com/link and type the code. Sign in with your email, then add your IPTV line.
Works on Chromecast with Google TV, Nvidia Shield, Mi Box and TVs running Android TV.
Search the Play Store for Downloader by AFTVnews and install it.
Open Downloader, type golku.com/apk and select Go. The TV asks once to allow installs from Downloader: allow it, then select Install.
Open Golku from your apps, scan the code with your phone and add your IPTV line.