I am trying to use the pressure option when using a calligraphy brush but the option is grayed out.

[#1]

I have Illustrator on my HP computer. I'm new to this app. I'm trying to use a calligraphy brush with the pressure option, but it's grayed out. The only ones I can select are fixed and random. I tried uninstalling and reinstalling Illustrator but that didn't work. I've been looking at what solved other people's problems and many of them have installed a Wacom driver, but I do not know what this is. Can someone please help?

[#2]

I have Illustrator on my HP computer. I'm new to this app. I'm trying to use a calligraphy brush with the pressure option, but it's grayed out. The only ones I can select are fixed and random. I tried uninstalling and reinstalling Illustrator but that didn't work. I've been looking at what solved other people's problems and many of them have installed a Wacom driver, but I do not know what this is. Can someone please help?

[#3]

Drivers are apps that allow the tablet to work with your computer. For Wacom, you can find your drivers here: https://www.wacom.com/en-dk/support/product-support/drivers