Login into Salesforce android application using Trailhead account

Question

I am beginner in salesforce. I am using my Gmail account to login to trailhead account. I want to login to salesforce android mobile app using this account. How can I do that ?

I have tried logging in directly using my Gmail ID and Gmail Password in its android app but it says username and password is not present. Please note that I haven't created any separate account in trailhead. I am just using my Google account to login into trailhead and want to login with the same account in salesforce android mobile app

This may be a general question, but I am new to this hence not sure how to do this. I googled and found many links explaining to login using trailhead account. It mention simply login with your trailhead ID and password. However, I am login using Google account hence I don't have any password. I simply select login using Google and it ask for google password when I am logging in on trailhead