This is an accepted solution.
Karlie here from the Shopify Support Team! If you're looking to use the app, Mega Menu, then you can install the app from the app page in the Shopify App store, here. If you're having difficulty installing the Mega Menu app, then you can always take a look at the app developer website for instructions or guides. You can check out the FAQ site for installation guides, here. Because Mega Menu was created by a third party app developer, Globo, you would want to reach out to Globo if you had any questions or difficulties with this app. You can always reach out to app developer by using the 'Support' section of the app page in the Shopify App Store.
It sounds like you're wanting to create some nested menus or dropdown menus in your store. If that's what you're looking to do, then you can always manually add in a nested menu by following our step by step Shopify guide, here.
If you're looking to add a contact page to your Shopify storefront to allow your customers to reach out to you with any questions they have, then you can do so by following this guide or by following the below instructions:
I hope this has answered your question. If not, or if you have any further questions please let me know. I will be happy to help!