That depends on what you actually need (e.g min quantity, max quantity, quantity step etc.). For example, let’s say you need to set min quantity for all products to 5, then:
1. Go to “WooCommerce > Settings > Product Quantity > Minimum Quantity”.
2. Check “Enable section” option there.
3. Set “Per item quantity – All products” to 5 and save settings.
So now your customers need to add at least 5 pieces of product to the cart to place an order.
If you could tell me what are your requirements, I could give you the exact instructions on how to achieve it. Also, if you wish, you can share an admin account to your server, so I could log in and help you with the settings (my email is [email protected]).