How to make people understand that a flat button is to be tapped/clicked

1. How do you make obvious that a button is clickable?
2. Should primary button be on left or right?

How do you make obvious that a button is clickable?

Apply clear visual cues to links.

Make it clear that links are clickable—avoid making users mouse over text to see if it's clickable. For example, make links blue or another color that stands out from the body text.

Should primary button be on left or right?

Full page designs should have the primary button on the left side of the page. If the browser window is large, or you have to scroll down to fill out a form, it's best to have the primary button right below the last bit of content on the page.