Hi Kykyfishy!
Is your side job as an employee?
If so, start with the TurboTax W-4 Calculator for 2023. I have placed the link below.
https://turbotax.intuit.com/tax-tools/calculators/w4
This tool will take into consideration income from both of your jobs to give you the correct results!
You may need to submit new W-4 forms to your employer(s) now, and you will want to go back to the calculator in December to make sure you have up to date withholdings for tax year 2024!
Have a great day!