If you get the Are you sure you want to do this? message after uploading the theme’s zip file via Appearance > Themes menu in your WordPress, it means that your server has low upload limits.
You may go around this problem in two ways:
- Install the theme using an FTP. The process is described in the Installing theme article.
- Increase the upload limits on your server, described below.
Below are the recommended values for specific options in your server configuration:
- max_execution_time 300
- memory_limit 256M
- post_max_size 128M
- upload_max_filesize 128M
If you are not familiar how to change those values in your php.ini file then please contact your host/server provider about it. They should change them in an instant.