How to add a header and a footer and alighn text?
You need to learn CSS. You just started CSS to learn and asking this thing.
<header> and <footer> tags provided in html5 are the semantic tags, which means that the browser will understand that the content within those elements has a special purpose. But those tags don't provide styling at all, it's up to you, to use CSS and position them accordingly, so you got to learn those styling properties first, and then if you get the problem, then this community is here to help you.