First let us congratulate you on the birth of your child!
The birth of your child does not automatically restart your cycles, so from a charting perspective, it is not the beginning of a fertility chart.
In general it takes a few weeks to a few months for your cycles to restart after birth depending on whether or not you are breastfeeding.
We recommend to wait until your first period postpartum to start fertility charting again. The birth is not a charting event per se so it is not recorded on your fertility chart.
Technically, you can start observing your signs right away but they may not be reliable and you may observe many false starts before your cycles resume fully.
Check the data menu/Charts Management to start a chart at an arbitrary date.