Log into your Moodle admin account, enable editing in Administration → Front page settings and click on Add an activity or resource on the top-right (next to Login).
In the lightbox, go to Resources (bottom) and select Page. Hit Add to progress to the edit section of your page.
In the page editor, add a title and description to your page. Inside Content, click to expand the buttons of your toolbar and look for the HTML button (symbol: <>).
When you have finished editing the page, click on Save and display, on the bottom, to view your online form from the student’s perspective. That’s it. Your students can now submit your form on Moodle and all form data will be sent to your 123FormBuilder account, in the Submissions section of your online form.