If you can’t access your admin pages, you’ll need to use an FTP client (like FileZilla), or your host’s cPanel (or File Manager) and navigate to the plugin on the server.
In your WP installation there, find wp-content/plugins and find and delete the problematic plugin’s folder (the one you updated). Hopefully that should allow you to get back into WP admin. Once done, you can try re-installing it. You may want to check the support forum for that plugin before re-installing though, to see if others are having the same trouble.
If this isn’t something you’re comfortable doing yourself, your web-host support would probably do this for you, or at least help you set up FTP access. Most of them also have help docs to walk you through how to use both FTP (or SFTP) and their FIle Manager.
