EV3 force sensor - how to download the block to EV3?
There is no force sensor in either the commercial or education version of the EV3 set, just the touch sensor for which there are standard blocks.
So I'm going to assume this is a sensor from an an external party. You need a file with extension .ev3b that can be imported in the mindstorms lab by clicking 'Tools' in the menu and then 'import block' which will open a dialog where you can browse for the file, and import the blocks in it.


Now to obtain that .ev3b file, you need to know from which vendor it was bought. Likely the file can be downloaded from their website. We could help you further if you could specify either the vendor or post a picture of the sensor.