I am an Uber driver, I would like to know when I input the expenses on the T2125 (like vehicle expense:fuel or maintenance), do I have to subtract the hst?

As an Uber driver you should have a GST/HST number and be claiming input tax credits on your remittance forms with CRA separately from your personal tax return. As the sales tax is then rebated to you it is necessary to remove the tax from your total expense amount.