You might try manually installing the theme or plugin. This can be done by using an FTP client such as Filezilla and entering the FTP information provided by the hosting company. Then, upload the theme file to the ‘Themes’ folder. The path from the WordPress root should be:
wp-content -> themes
or
wp-content -> plugins
After that, you should be able to activate from the WordPress admin screen.
You have file permission issues in your WordPress directory. Just make sure that they’re set correctly and everything will be fine. Now please note that some hosts will still block this regardless of folder/file permissions due to their poor server security by not allowing any direct installation without login credentials.