Please how can i click this button?

Hello again guys,

Ill try and make this quick as im my brains starting to melt, ive tried aloooot of combinations to try and click the following button, can som1 please just give me a quick few lines that will click the following? Thanks alot guys

<BUTTON class="action af_commandButton" onclick="submitForm('ManageUsers',1,{source:'_id106:_id133'});return false;" type=button>Assign</BUTTON>

Thanks again

Ant