IHM CVI and creation DLL

Hello;
I work on Project to which I must add some functionality, indeed I work on a test bench that allows to test radio modules and check their calibration and display information in the ihm, so I would change my HMI and add Of the functions to create a dll at the end, there's quite a thing that I can not understand since it is not I who created the project at the beginning and it is the first time I work On teststand and cvi, so let me ask you some questions:
 
1- What is the .fp file for?
2-How to make the links between the functions that will retrieve the data in teststand and display them in the ihm?