In the Ti Nspire, a folder called MyLib is available at the beginning of usage with the calculator. This folder contains programs which can be accessed through the documents inside this folder, making it a program library. (Duh :P)
You can also write your own programs and add them to the MyLib folder! Some basic programs for MyLib can be found here. After adding a program to the MyLib folder be sure to refresh your libraries, which can be done with:
[Doc] + 6 or [Menu] + B
If the program is set to LibPub it can be accessed via the catalog, which is that little book-like button below [Del] If it is set to LibPriv then you can access it by typing in a calculator page (or scratchpad):
“Document name”\”program/function name”
So if your document is called Chemistry and your program called Balance it would be:
Hope this helps!