If you've ever wanted to write code on your Android phone, or work on files on your laptop while you're standing around somewhere you can't pull out your laptop, this is the way to do it!
On your Android phone, please install F-Droid. You'll need to download the APK and open it. If it asks you whether you want to install an "unknown app", allow it. Then, in F-Droid, search for "Termux" and install the "Termux" app.
Alternatively, you can download the Termux APK by itself, but it won't auto-update.
Now, you're ready to follow with this guide. Please follow this guide on a secure network, as it will temporarily leave your devices open to network attacks. Once you've finished the setup process, it will be safe to use on insecure networks.