Start by reading the "How to Use" page:
Each photo effect or text effect has its own page in the site. Since there are thousands of effects, depending on the kind of effect, you need surf to an "effect list page", where you choose an effect style by clicking the related example image. When you get in an effect page, you can calculate the effect, so the result appears in the "result page". In such result page you can download the effect you created or go back to change the effect configuration or to try a new effect.
The "effect pages" (the pages where you configure and calculate an effect) have a "Configuration" section and a "Generate" button (you click this button to start calculating the effect offered by the page). Below there are some examples:
To choose among the many photo effects, you can start here:
To choose among the thousands photo effects, you can start here: