Hi, Yes you do need to advise on your application your overseas travel dates. You can update your information online through your application to add your travel details. As your application will clearly state your travel dates the department will be fully aware you are overseas during that time and will not arrange any appointments during that time.
Next stage is your interview and citizenship test date, which is all done at the same time.
If you are unsure how to update online application you may be able to receive help by calling.....