If you go into themes through your back office ,there you will find a selection of themes to choose from. Scroll through them, you can hit the demo button and it will show you what your website would looks like if you were to use the theme template, It will also tell you information, for example, what plugins are compatible with that theme, If you find one that fits your website then hit apply, and your website will adapt to your new theme. hope I was helpful

Kyle will walk through themes in the training if you have not gotten that far yet.

But, when you log into your WP back end, you got to Appearance>Themes>Add New and then you will have options to choose from.

I do recommend following along in the training though.

Here is a webinar on the topic as well, if you are interested. Changing WordPress Themes

Hi,
Jay has done some live training on this. Here is the replay. This will help you :) Changing WordPress Themes Debs :)