To generate an application layout file that includes links to Bootstrap, Font Awesome, and some boilerplate markup for a nav bar and alert messages, run the command
rails g draft:layout
It will warn you that it is going to overwrite your existing app/views/layouts/application.html.erb – say yes if you are sure that’s okay. Copy out any important stuff if necessary, to be re-pasted back in.
As with all generators, I recommend making a git commit before you generate, and then compare the diff at /git. What files did it add? What are they doing?