Important: due to limitations with the Wix platform, the address autocompletion feature of the lead form does not function on Wix websites at the moment.
The first thing you need to do is place an "HTML Code" element on your page. To do this:
Click the "+" icon in the navigation bar on the left
Click "More" all the way at the bottom of the menu
Finally, click the "HTML Code" icon
Now that you've installed the HTML element, you need to add the lead form code to it:
Click the "Enter Code" button
Select "Code" from the popup
In the text area, paste your code that you copied from the Settings > Leads > Wix Installation
Finally, click the "Update" button
You should now see the form in the Wix Editor. At first, it may appear very small. You can use the handles on the element to adjust the size.