robots.txt configuration

Hello,
I’ve just installed AIOSEOP and I’m dealing with the robots.txt file. Could you please help me with the following:
1. Do I have to set up the robots.txt feature, or my website has one already?
2. Is the following file ok, or should I add something else?

User-agent: *
Disallow: /wp-admin/
Allow: /wp-admin/admin-ajax.php

Sitemap: http://canadaimmigrants.com/sitemap.xml

Kind regards,

1question

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