You can add a new cost centre to your Chart of Accounts directly in Dimensions.
Click the Financials tab.
In Records, click the Set Up menu and choose Cost Centre.
Click Edit in the main ribbon.
Scroll to the end of the list and click the last entry.
Press the Tab key twice to create a new empty line at the end of the list.
Enter your cost centre code, name, and short name, then press Tab. Repeat steps 5 and 6 to add further cost centres.
Click Save.
Return to the Chart of Accounts and click Add. Your new cost centres are now available for selection.