After installing EcomSolid theme, you can link any pages you created by Shopify to your menu by following this tutorial or several steps below:
Step 1: Log in to your Shopify dashboard (through this link: your-store.myshopify.com/admin) and click on the “Pages” section.
Step 2: Open the page that you want to link to your menu, then click on the “View page" button below your page name.
Step 3: After that, copy your page link (which will appear on the new tab after you click on “View page")
Step 4: Login to your EcomSolid dashboard, click on the "Customize" button at the right top of your page.
Step 5: Once you are here, scroll down to the bottom of your page, you will see your mega menu in the footer. Click on the menu category that you want to link your page to.
Step 6: After that, click on the wheel icon next to your menu category --> Click on "Pick a link" button --> Paste the link (you copied from Shopify page) into the "Custom URL" box --> Then click on the "Save" bottom.
When you're done, just click on the "Update" button at the right top of your page and now you have successfully linked a page you created via Shopify to your menu.