1 - Install wordpress on your hosting / domain.
2 - Set up you theme with a child theme ( child themes are important for future updates so that you don't loose all your customisations)
3 - Set up your theme to look exactly like the demo (This makes it easy for you to customise your theme so that you can just edit what is there rather than add a design from scratch)
4 - Update and Secure. Add security and make sure all plugins, themes and wordpress core are up to date. (This is extremely important if you don't want to get hacked)
5 - Set & forget (Set updates to automatically take place so that you don't have to do this manually on a continuous basis)
6 - SEO (Optimise your theme for seo)
7 - Speed Optimisation (Get your site running fast)