Thank you that makes more sense. To recap my (non professional) understanding for anyone else in a similar situation.
All that's needed is to update from single to married filing jointly - this will automatically take into account the standard deduction for married filing jointly.
If needed you can observe how your withholding changes after this update and use the IRS w4 calculator to calculate any additional withholdings as there are no time restrictions on when you can make adjustments.
