You can use the following methods to install a WordPress theme:

Install using the dashboard:

1. Go to Appearance in your WordPress dashboard
2. Select themes
3. Click on Add New
4. Check the available themes
5. Click Details & Preview to discover more about a given theme
6. Click Install to add the theme
7. Click Activate after installation to change your theme
    

Install using a ZIP file:

1. Go to Appearance and then open Themes
2. Click Add New, then the Upload Theme button
3. Select your ZIP file, then click Install Now
4. Once installed, click the Activate button

Upload using FTP:

1. Obtain your web host's (S)FTP credentials, including your server, password, and log in ID
2. Go to your website using an FTP program
3. Go to the /wp-content/themes/
4. Upload the theme folder that was unzipped
5. Go to return to the WordPress dashboard and select Appearance > Themes
6. Find the theme you uploaded and select Activate