How can I change the tax amount withheld from my paycheck?

This is the W4 needed to change your tax withholdings.
Print out a copy, fill out your information (it has instructions and a worksheet to help calculate the number of allowances you are claiming), sign it, and bring it into Rob Winberg in accounting.
You only need to submit the first page.
Rob also has copies and can help you fill out the form if you have questions.