The way DeepL works is pretty simple since it's in development, but it still offers excellent results. To translate any text, all you have to do is enter the text in the first box and choose the language. Then, the box right below it will show the translated text.
DeepL is designed so that, by hitting Ctrl+C on your computer, the copied text is pasted and translated automatically. So you don't have to copy text, open the application, and then copy the translated text after that. Instead, you can copy the text, and the application will open itself to translate it. The main limitation is that it only translates into eight languages: Spanish, English, German, Portuguese, Italian, Dutch, Polish, and Russian.
DeepL is an incredibly useful tool for translating text quickly with amazing results. Like any other translator, this one is subject to occasional errors, but it's still one of the most accurate translators out there.