I am really new to this Arduino stuff. I can't figure out one of my problems on my own.

I am using this 2.4 TFT display shield on an Arduino Uno. It works fine so far: I have coded a little sketch for it that displays a start button and after tapping that it shows random colors.

Now I would like to connect a circuit with jumper cables that are used as sensors. When I touch one of the jumper cables the light connected will turn on.

The problem I have now is that this specific circuit is using an other Arduino because my first Arduino is already 'full' because the TFT shield is taking up all pins.

How can I resolve my problem? Is it possible to Stack Arduinos? Is it possible to connect those Arduinos somehow? Thanks in advance!