This is the badge our junior students get when they pass their first grading.
It is worn on the left sleeve of your uniform. 

Before your first grading you will need a uniform.
In aikido we wear white uniforms.
You may wear a white T shirt under your uniform.
Always cross the left side of the jacket over the right side.
You will be taught how to tie your Obi (belt) correctly.
You can also find the instructions on the web site
Your uniform should always be clean and tidy and the ends of your belt even.

This picture was done by a student who was 8 years old at the time.