When opening the terminal, can't input

[ItsSven64]

I opened the terminal but i cant input any characters. A guide on how to use this program would be useful, because im surely missing something

[commandblockguy]

The terminal reads writes input to and displays output from a USB serial device or host. If you don't connect the calculator to anything, or connect it to a device which is not outputting anything, you won't see anything on the screen. Most operating systems do not do anything with serial devices by default (including echoing characters that you type back to you), so you'll either need to write data to the serial device yourself or configure your OS to attach a shell to the serial device.
I'm not too familiar with Windows, but the calculator should show up as a COM device, which you can then write data to and read data from.
On Linux, you can access the terminal at /dev/ttyACM0. For example, you could output characters to the terminal with echo "Hello World!" > /dev/ttyACM0. On most popular distros, you should be able to get a login shell on the calculator by running sudo systemctl start getty@ttyACM0.