how to install / reference Simplepie.php

[seandisanti]

have you looked at the file "class-simplepie.php" in the /wp-includes/ folder?

I'm not familiar with it myself, but it sounds like it has the functionality you seek. i would explore the file to get function names etc and once you've found what you're looking for, go to appearance>editor>header.php and add a require() or include() for the file and update your function calls to the new function names

[seandisanti]

step one is identifying the deprecated functions that you were trying to use initially. Then identify what they do, hopefully the function names will be descriptive enough to remove a lot of the guesswork there. then browse through the code or documentation for the class-simplepie.php for functions with similar names. in the event that function names in one or both files are less than helpful, you can write up signatures for the deprecated functions; name, input parameters, return value and type. then go through simplepie looking for similar signature. Or you could just google for documentation, but I assumed you had already done