Force Yahoo app to ask for my password.

The first time I accessed my email with the Yahoo app for Android, I was asked to enter my Yahoo ID and password. Since then, the app takes me directly to my Inbox. For security, in case I lose my phone, I want the app to ask for my password every time. Does anyone know how I can force it to ask?

The official Yahoo help site for Android has a contact form - Help for Yahoo Mail app for Android

I have an iPhone, they can better help with this question. Please share the solution if it's possible to require your password when you reload the app.