Open the 
Dimensions
window.
Select the dimension and then click Dimension, Account Type Default Dim.
Fill in a line for each new default dimension you want to set up. For Help about a specific field, click the field and press F1.
You can set up a default dimension for an account type. The program will then copy this code to the journal, sales or purchase line when the account type is filled in on the line. However, you may delete or change the code if appropriate.
Open the Dimensions
window.
Select the dimension and then click Dimension, Account Type Default Dim.
Fill in a line for each new default dimension you want to set up. For Help about a specific field, click the field and press F1.
If you want to make a dimension mandatory but you do not want to assign a default value to the dimension, leave the Dimension Value Code field blank and then select Code Mandatory in the Value Posting field.
If an account is going to be used in the Adjust Exchange Rates batch job or the Post Inventory Cost to G/L batch job, do not select Code Mandatory or Same Code. These batch jobs cannot use dimension codes.
If an account must have a different dimension assigned to it than the default dimension already set up for the account type, you must set up a default dimension for this account. The default dimension for the individual account then replaces the default dimension for the account type.
Setting Up Dimension Combinations
Setting Up Default Dimensions for One Account
Setting Up Shortcut Dimensions