Applying for special consideration is not the same as simply asking for an extension from your tutor/ lecturer or subject coordinator. If you need a week (or less) for an extension for an assignment, talk to your tutor or subject co-ordinator first to request an extension to complete your assignment. If you have valid grounds they cannot unreasonably refuse you an extension.
If, however, you need more time, or you feel that you need to explain why your academic performance has been affected, then fill out an application for special consideration online.