How do I reinstall the Tango app on my iPhone after deleting it?

You mean this one?

https://apps.apple.com/us/app/tango/id6502249418

As mentioned by Kurtosis, just redownload it from the App Store again.

If you mean some other App, that is not available, then you won't be able to get it again.

Go to the App Store and install it like you did the first time you installed it.

It is no longer available in the App Store, so you will not be able to download it again. When apps are removed from the App Store, either by Apple or the Developer, they will remain on your device, but you will not be able to download it again.

I suspect it was the Tango Live app that has not been available for a very long time now. Access is available on their website here.

Tango Live

There have been many other posts in these forums about that app:

How can I download Tango for my iPhone if… - Apple Community