Hello, please see below link for assisting to your withholding. Hope this helps
Firstly, congratulations on the raises!
It is important to inform all payroll systems that you have multiple income sources and how much is being earned outside of each respective payroll. When completing the W4, there is a section called "Step 2: Multiple Jobs or Spouse Works". This is where you will tell your respective payrolls of the addition earned income. This will have the payroll systems look at your aggregate income and calculate your expected tax brackets in order to more accurately withhold. I would also recommend you complete Form W-4P so your payer can withhold the correct amount of federal income tax from your pension as well.