How do I use sensors with a TFT?

not the programming, physically.

I have this TFT screen and it connects directly to an arduino mega without any additional shield. https://www.itead.cc/itead-3-2-tft-lcd-touch-shield.html

but it uses all of the pins except ioref, SDA and SCL (I don't even know what those are)

so how am I supposed to connect sensors to the board?

Hi.

SDA and SCL form the I2C bus. You can connect up to 127 devices to a bus if i remember correctly (maybe i'm mistaking with some other bus here like USB). Anyway, you can connect a lot to this. Look for sensors that use I2C, (sometimes called TWI because of trademark issues). There's a lot of those available.

I doubt it uses all of the pins. It may occupy them all, but if you really want access to some pins, you'll have to figure out which ones aren't actually being used. Looking to see which ones aren't connected to anything on the board, serial monitoring them for activity, running a bunch of female-to-male cables between the LCD and the Arduino so you can disconnect pins to see which ones don't change function, get creative.

I think I can use this right? http://www.dfrobot.com/index.php?route=product/product&product_id=60

Go to the product page of that display of yours. Find the technical details page of it, and find out that it doesn't use all pins. Also see the part where the SD card interface is mentioned, might come in handy if you want to create a logger for your sensor data.

MAS3: Go to the product page of that display of yours. Find the technical details page of it, and find out that it doesn't use all pins. Also see the part where the SD card interface is mentioned, might come in handy if you want to create a logger for your sensor data.

I figured it didn't actually use all the pins, but I can use the protoboard I linked above to access the usable pins more easily right?

would it allow the use of 11 or 12 PWM channels?