It's explained in the in-program 'help' file. I don't have in front of me as I type this on an iPad but, as far as I can recall, as long as you have added APPGRAPHICS using the SF Package Manager, you just put, USE APPGRAPHICS near the start of every program which uses this library then put in as many sub program CALLs to the library as you like.
In case this doesn't work, you may need to provide some settings in the SF project options. To find out what, if anything is needed, use the SF startup page to open one of the relevant examples, and look in the project options for the example you have selected.
If the above is all cobblers then I'm sure one of the other regulars to this forum will chip in with correct advice.
I hope you get it working because Jeff's APPGRAPHICS is a fabulous extension to SF, which, at a single extraordinary stroke, catapults SF from nowhere, fully into advanced Fortran-for-Windows programming.
By the way, the SIGSEGV problem I had when using the debugger to examine code containing a call to th DISLIN library to display a file selection dialog box, remains a problem when using a cal to AppGraphics to do the same thing. On present evidence, it seems most likely that there's a bug in the 'DBG' debugger, not in SF, which is causing this. It does not impede use of the file selection dialog in programs. It just crashes the debugger.
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John