1. Make sure you have to purchase an additional seat to your current Pro 2018 license. not just purchase a new license of Prp 2018 with different codes. Afaik, you have to purchase from one of limited resellers for additional seat (e.g 2017-2019).
2. The “Custom and Network options” setting lets you choose where to install QuickBooks on your computer, install the program and share a company file with others, or set up the computer only to share the company file If you selected the “Custom and Network options” setting, choose a setting on the “Custom and Network Options” screen, and then click Next. On the second computer, select “I’ll be using QuickBooks on this computer.” This option installs the program on your computer and will access to your company file in the first computer later.
https://quickbooks.intuit.com/learn-support/en-us/configure-for-multiple-users/set-up-and-install-a-...
Hope it helps.
