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, login to your Weebly editor.
Find the area/page you wish to add the Studio login form to, then from the left-hand module options look for 'Embed Code' and drag'n'drop this onto your page where you want the login form to be. Circled in red below is what you're looking for:
Click on the new widget, then 'Edit Custom HTML':
Copy/paste in the following code from 'Step 2' then add:
<div id="studio-member-login"></div>Next, click on ‘Pages’ in the top menu:
Select the appropriate page, then select 'SEO Settings' as seen above.
In the 'HEADER CODE' section, copy/paste in the code under Step 1 in the Studio Login Form Integration:
Save & Publish your changes and check out your website, you should now see the Studio login form where you placed it.