How to Login WebSite via Android Application?

Because I can't save my Id, Pw ..on the website, I'm trying to create a Application for One-Click Login. WebSite url is "https://m.people.mcd.co.kr/main/login.do

I already made Computer Program doing same job, but it's really hard for me to create Android Version.

What I Succeed is

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1. To Make WebView

2. To input my Info

3. To Save my Info In App

What I need is

1. The Way to Login the website, clicking a button in App : But How???