Log into your Donorbox dashboard and click on the "Edit" link next to your campaign form.
Go to the Advanced tab and select the checkbox marked "Collect Address". This will add the address field to your form for donors to fill in their address. Click Save when you're done.
You can choose to make this optional for the donor. If it is optional, the donor will see the address field, but will not be required to fill it out.
After you've enabled the Address field, your donors will see the address field in the Information tab of the donation form, as shown here: