Within Dimensions please carry out the following process:
Click the Financials tab.
In Records, select the Set Up menu and choose 'Cost Centre'.
Click Edit in the main ribbon.
Scroll to the end of the list and select the last entry.
Press the Tab key twice - this creates a new empty line at the end of the list.
Enter your Cost Centre code, name and short name as you require followed by the Tab key. You can repeat steps 5 and as necessary.
Click Save to finish.
Return to the Chart of Accounts, click Add and the new Cost Centres will now be available for selection.