Set the form's "data entry" property to true.

You can set the Form's Data Entry property to Yes, as Rbear3 suggests; this
will work but has the disadvantage that you cannot then use the form to see or
edit existing records.

An alternative is to open the Form in design view. View the Form's Properties;
on the Events tab find the Load property. Click the ... icon by it and choose
"Code Builder". Access will give you a Sub and End Sub line, just add one
more:

Private Sub Form_Load()
DoCmd.GoToRecord acDataForm, Me.Name, acNewRecord
End Sub

            John W. Vinson [MVP]