How do I enter receipts that I already used cash from daily sales income for?

Treat the till as a separate Cash bank account. Many people call this Petty Cash but Cash on Hand or Cash Drawer works as well. You want to essentially track this cash separate from banking. You can pay expenses from it by posting checks or expenses (online only - note your question although tagged as online popped up in the desktop question arena) When you are creating your daily cash and checks deposits to banking you will post cash back to your till account to reflect what was used.

Quick example. You maintain $50 in cash drawer at end and beginning of each day. During the day you sell $500 but have to pay out $100 in cash expense. Your Undeposited Funds account shows $500 to deposit. Select the 500 but post 100 cash back to the drawer. And if by chance you end the day with more or less than your normal 50 you adjust that also.

Additionally any cash you remove from banking g at an ATM also goes into same cash on hand account where you can record expenses

Greetings, @LThorsen1.

QuickBooks Online has an option to track any purchases that you have in your account. Let's set up and create a Product and Services you can select either of these four types it depends of the nature of your account. 

• Inventory items: Items you buy or sell and track quantities for ( You must turn on the Tracking Quantity on Hand option to track Inventory items)
• Non-inventory items: Items you buy or sell but either can't or don't need to track quantities
• Services: Services you provide to customers, such as landscaping or tutoring
• Bundle: A collection of products or services you sell together

Here's how to create Product and Services: 

1. Go to the Gear icon, click Product and Service under Lists.
2. Select New, choose types of accounts. 
3. Add a name, SKU, or category for what you're tracking. 
4. Complete the necessary boxes. 
5. Click Save and close.

I've attached a short video for your further reference: How to Set Up Products & Services: Non-inventory, Service Items, & More.

Once you’re all set up, you can easily track what you buy or sell. Here are helpful steps if you want to update types: Change Product and Service types.

Keep me posted if there's anything else you need. I'm just a post away. Have a good one.