There are two different problems you need to solve here:
1. Converting from mV/V to pressure or weight
Load cells provide an output of mV/V (i.e. for each volt used to power the load cell, it sends back a certain mV proportional to the amount of strain in the load cell). In order to convert this to a meaningful unit, you must calibrate the load cell with a known value. For example, if you want it to measure weight, you can place an object of known weight on the load cell and take note of the mV/V. Then measure the mV/V with no weight on the load cell. Using these two points, you can create a straight line that you can use to convert any future values to a weight. You can find a more in-depth guide of this process here
You should recalibrate often for most accurate results.
2. Displaying the converted value on your screen
Phidgets are intended to be tools for people who don't have a lot of electronics expertise, but do
have some programming knowledge. If you use our sample code, you'll get a basic program that prints the value to the screen, but it won't be converted. You'll have to modify the code to convert the value as described in the calibration guide I linked above. If you can't get our code samples running at all, try to find someone who knows programming and download the sample in the programming language that person is familiar with.
I hope this helps. Let me know if you have any other questions.