Changing Theme

I have made a sub-domain and copied my site to it.

I want to rebuild my site. I have found a theme I like ‘ColorMag’ and downloaded it.

I know how to activate the theme but when I do it shows my original site. How do I get the new theme to show with all its wording/pictures etc so I can change the words/pictures to what I want.

The page I need help with: [log in to see the link]