When you installed it successfully, please go to Settings of your WordPress admin area and find Estatik Mortgage Calculator there.
You will get settings tabs, click one by one and configure it according to your needs.
To display it on frontend, please go to Appearance >> Widgets and find there Estatik Mortgage Calculator widget. Grag and drop it into selected Sidebar. Click Save.
Check your frontend, calculator must be displayed there.
In case if there are still any questions or issues, please contact us and we will help you.