how do i put something in the icon composer?

Instructions for submitting work to the icon assembler appear on the icon assembler's main page along with other details on labeling layer groups, etc..., in the comment section.

If you do not understand the submission process or the work you submit is amateurish you could be wasting both your time and the administrator's. You should aim to create a submission that is of the same quality level of the majority on display. You should ensure that you have researched and understand all available information regarding the creation and submission process.

It might be best for you to start with creating your own icons first before you attempt to create something for the icon assembler.