STEP 1: In Studio, go to Settings > Member Area > Website Integration > Login Form Integration:
On this page you'll see a number of steps, ignore these for now, but you'll need some of this information later.
STEP 2: In a new tab/browser, log in to your WIX editor. Find the area/page you wish to add the Studio login form to, then from the left-hand module options, look for 'Add Apps':
Browse down and find 'Embed HTML', click on it and get the app:
Click the '+ Add to Site' button:
Select the 'Enter Code' button, now on your page:
In this HTML box, copy/paste in the code under Step 1 in the Studio Login Form Integration:
Save and Publish your changes.
You're done!