On the login page, just click the link called "Continue as "guest" without logging in". It is just below where you type your user name and password.
On the next page, you will see a list of all the bugs and feature requests that have been submitted to APSIM. Both by internal staff and external users such as yourself. It is suggested that you take a look at this list to see if someone else has already submitted the bug or feature request already. In the top left corner (as you look at it) click a link called "add a new bug"
This is the page that allows you to submit a bug or feature request. In the Description field just type a brief description, In the Project field choose which product your request is with regard to. In the Category choose what type of request it is. In Apsim Version just type in the version of APSIM that you noticed the bug in (if your request is not a bug then just leave it blank). Finally in the Comment box, write a detailed description of the bug or feature request. IMPORTANT leave your name and contact details (you don't have to but if you don't and we don't understand your request or we can not recreate the bug we will not be able to act on it). When you are done, just click the Create button. Once this button is clicked you have sucessfully submitted your bug.
After submitting the bug you will be now taken to the update page for the bug you just submitted. You will see some links on the left hand side of the page (as you look at it). Most of these are irrelavent to you except for the "add attachment" link. You can click this to add any files or screen captures to do with your bug. You will also see your previously submitted comments underneath the Comment text box. If you want to add anything you may have forgotten to put, you can just type it in the Comment text box and click the Update button and it will be added to the bug.
If you click the "bugs" link at the top of the page, you will be taken back to the list of bugs page. You will notice that your bug has been added. If you click the link in the "desc" column, you will be taken back to this "update" page.
You can come back at any time and add more stuff about the bug. If you fix the bug yourself, or if you made a mistake and it wasn't really a bug, just log back in and you will be taken to the bugs page. Just click the link in the desc column for the bug you want to update to get to the update page for the bug and add a comment to the bug so we know not to worry about it. You can also add comments to any other bugs on the bugs page in exactly the same way. Not only the ones you have created.