Here’s a resource that answers that questions. It includes information about each error type and suggests fixes one-by-one: https://www.acceleratormarketing.com/trench-report/mobile-usability-errors-in-google-webmaster-tools/
It sound like you make have unchecked the box for “Allow search engines to index this site” during your installation process.
You’ll find a great guide on Robots.txt files, and instructions on using an awesome Robots.txt checking tool here: http://www.acceleratormarketing.com/trench-report/dont-let-robots-txt-block-site-webmaster-tools/
