I'm glad you asked this. There's a few ways of going about this.
If you're building a model-driven app, there's an existing CRM tool that will create translations and you can revise them in case they don't come out with the right context (ex: 'radio' control interpreted as an AM/FM 'radio' instead of its shape). See EasyTranslator:
Here's a blog about how to use a table to lookup translations from a table:
And here is my solution that gathers text from different controls and galleries on the screen, concatenates it, and translates it in one pass through Microsoft Translator.
Let me know which one you prefer.
Do you want to translate your PowerApps app into spanish language?
If you want to translate your PowerApps app into spanish language, I agree with @mr-dang's thought almost.
More details about creating multilingual apps in PowerApps, please check the following article: