Hello there, @The Real Swim.

Let me chime in and provide information about using QuickBooks Desktop (QBDT) on two computers at the same time.

To start with, you can install QBDT 2015 on the other computer. However, ensure to create a backup copy of your company file. Then, install and restore your file to the new computer.

Here's how to create a backup company file:

1. Go to the File menu, and select Switch to Single-user Mode.
2. Select Local Backup and then click Next.
3. In the Local Backup Only section, select Browse, and then select where you want to save your backup company file.
4. When you're ready, select OK.
5. Select Save it now, and then click Next.

After creating a backup, you can prepare for the installation of QuickBooks. Make sure that your computer meets the system requirements and download your version of QuickBooks Desktop. Save the downloaded file in a location that is easily accessible, such as a Windows desktop, Lastly, keep your product and license number ready for the installation process.

Once done, you can now install the QBDT. Here's how:

1. Open the file QuickBooks.exe.
2. Follow the on-screen instructions. Accept the software license agreement and then select Next.
3. Enter your product and license numbers. Then select Next.

To restore your file on your new computer, follow the steps below:

1. Open QuickBooks.
2. Select the File menu, then Open or Restore Company.
3. Restore the file based on its type:

• Windows company file (.qbw)

                a. Select Open a company file, then select Next.

                b. Open the appropriate folder, then choose the company file.

                c. Select Open, then enter the password.

• Windows backup file (.qbb)
• Windows portable file (.qbm)
• Mac company file (.dmg or .qbxxx)

However, if you want to use QuickBooks on both computers at the same time or use multi-user. Yes, you'll need to purchase a new license with one additional user. This will enable you to use QuickBooks on both computers at the same time. You may refer to this website to check for the pricing: QuickBooks Desktop Pricing. 

You can also contact the support team, to check for plans & pricing that suit your business: Contact QuickBooks Desktop support.

For future reference, you can check this article to help you learn more about hosting your company data in multi-user mode in QBDT: Multi-user mode.

Stay in touch with me if there's anything else I can help you with managing QBDT on two computers. I'll be right here to provide the information that you need.