How do I convert a file into an app?

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Sorry, your question makes absolutely no sense.

JosephCoolDad wrote:

That’s rude

It's the truth.

Your question makes no sense.

You can't "convert a file to an app"... Unless, of course, the "file" is the source code for an application you've written, in which case you would compile the source code to produce and executable application... but I would assume that anyone who could produce such a file would know how to do that, or at least what had to be done.

Since I'm guessing that's not what you mean, you need to rephrase your question, providing enough information for us to be able to know, or at least have a clue, as to what you're talking about.