pad and pin numbers are changed with the pin or pad properties dialog. (right click context menu of the pin or pad -> properties. Or hotkey e while your mouse hovers above the pad or pin. Use the symbol or footprint editors for this task.)
The footprint assignment can be done in multiple ways. Either assign the footprint already in the library, or do this task sometime before switching to the pcb side of your design task but after placing the symbol into the schematic. (There is also an experimental option where you select the footprint while placing the symbol in eeschema.)
Both workflows make sense for different components. I typically assign the footprint for simple devices like resistors and connectors at the end of the schematic design process while i have the footprint for more complex devices already pre assigned in the specialized symbol for this part. You might prefer either of these work-flows or like me a mixture of them. There is no wrong or right here. (The good news: KiCad is flexible and allows for different workflows. The bad news: KiCad is flexible and expects the user to decide which workflow they like for their current task.)
My workflow allows having a single resistor symbol for all resistors instead of needing a resistor symbol for at least every used resistor size. While it still reduces the chance of doing something wrong with more complex devices. (Assigning footprints at the end is like any user interaction a place where an error can occur. Having trusted symbols with pre assigned footprints reduces this risk.)
In more detail: How can i assign a footprint to a symbol?