How to add a new theme on WordPress

You can download any theme from the Theme Directory directly to your site by following these steps:

Log in to the WordPress admin dashboard, example: yourwebsite.com/wp-admin
Select the appearance, then themes.
Click on Add New.
Either use the Search or Filter options to locate a Theme you would like to use.
Click on the Preview link to preview the Theme or the Install link to upload the Theme to your site,
Or use the Upload Theme button at the top of page to upload a zipped copy of a Theme that you have previously downloaded or bought. Example if you purchased a premium theme from Themeforest.net