You can create a Popup form, and link it with a menu button on your Shopify store.
Follow the easy steps mentioned below:
Step 1: Click on the Apps tab in the Shopify admin panel, and open your MailMunch -Email Popup app.

Step 2: Navigate to your Mailmunch menu bar items on the homepage, and select Campaigns. Click on the Create New Campaign button present in the top right corner of your screen.

Step 3: Click on the Form/Popup option from the different campaign types displayed, and then select Popover from the different form types displayed.


Step 4: Select an attractive template. Design and customize your campaign to your liking. In the Publish step, copy the Trigger on Click code.

Step 5: Open the admin panel of your Shopify store, click on the Online Store -> Navigation. Click on the Main Menu or the Footer Menu.

Step 6: Click on the Add menu item option.

Step 7: Enter the menu Name and paste the code you copied earlier in the Link tab. Click on the Add button to apply changes. Then, click on the Save menu button.
