We normally advise adding projects to your portfolio before customising your theme as it makes it easier to see your changes. Below is a little cheat sheet to familiarise you with customising Poplin.
Cheat sheets are available for all themes in this help section.
Important note: When customising your site and checking the results in your browser you may not see your changes. If this is the case your browser has cached the previous version to reduce bandwidth demand. You can force the browser to take a new copy by hard-refreshing your browser, or by clicking the View Site link at the top right of your Fabrik screen to open a new tab.