Don’t worry, everyone feels lost when they first join. It’s all confusing and new, but the plebs have got your back. I just looked through the Cash App FAQs and it looks like you can create one time invoices but not a permanent address to your Lightning Wallet that you can put in your profile. If you do want a permanent address you’ll need to use another Lightning Wallet. Wallet of Satoshi is quite good, especially if you don’t have your own Lightning node.