Aheto can be uninstalled in two ways: from the plugins page in WordPress admin, and manually through FTP/File manager.
From WordPress admin
You can uninstall Aheto as any other plugin.
To do it, log in to your WordPress admin panel and go to Plugins and click Deactivate.
After clicking that link, you will be asked why you are deactivating plugin - choose the answer and click on Submit & Deactivate
Then click Delete.
The manual removing involves delete aheto folder from your webserver through a FTP software.
Go to folder to wp-content/plugins directory and remove aheto folder.