Rails App configurations for AWS CodeBuild

I have a rails application that is deployed on AWS EC2 instance with CodePipeline. I have added the Build stage in the pipeline using AWS CodeBuild to build test my code.

I have no idea about where to add below rails command to execute whenever code auto-deploy using the pipeline.

1. bundle install
2. rake db:migrate, create, assets compile
3. Restart sidekiq

LOOKING FOR SOME ANSWERS FROM EXPERTS.
I DO HAVE A BUILDSPEC.YML FILE AND MY CONTAINER BOOTS UP AND SAYS:
Your Ruby version is 2.6.5, but your Gemfile specified 2.7.2
my ruby version of the app is not 2.6.5 it's 2.7.2 I don't why it's not working :(