The first payment of the PAS (withholding of income tax) should have been done yesterday.
Don’t hesitate to look at your company’s bank account or your impots.gouv.fr account to confirm it.
If it has not yet been done, it should be in a few days. In any cases if it is not done by the 22nd, French Payroll Expert strongly recommend that you contact the fiscal administration to see if it is normal.
If it is not, you can generate a manual direct debit from your impts.gouv.fr account.