I live in Virginia and just started working in Maryland. I am being asked if I need to fill out the VA-4B for for employee credit for income taxes?

Virginia and Maryland have tax reciprocity.  VA residents are not subject to MD income tax on their W2 income.  The correct form for you to fill out and submit to your employer is MD Form MW507.  This will alert your employer that you are a VA resident and not subject to MD withholding.  Here's a link to the form:

https://www.marylandtaxes.gov/forms/current_forms/mw507.pdf

VA-4B does not apply in cases of reciprocal states.

You should give your employer a Maryland Form MW507 so they will not withhold Maryland state taxes - https://www.marylandtaxes.gov/forms/current_forms/mw507.pdf

The employer should only withhold Virginia state taxes from your wages.

TurboTax support FAQ - https://ttlc.intuit.com/turbotax-support/en-us/help-article/state-taxes/states-reciprocal-agreements/L4JKSLqpR_US_en_US?uid=lchy7qvg