To install a package, proceed as follows.
(1) Create or identify a directory (folder) where you will keep the mla file(s) and the help file. Copy the mla and help files there.
(2) Open Maple, at the prompt type libname. This will display where maple currently looks for packages. You need to modify libname to include the path to the directory used in (1). This can be done by assigning libname := newpath, libname;.
(3) If you are installing the DifferentialGeometry package: Execute with(DifferentialGeometry) to load the package. At the prompt execute DGbuild; and verify that the build number matches the build displayed on this website. This step can be ignored if you are installing DGApplications.
(4) Step (2) can be automatically executed at the start of every Maple session by adding the libname assignment to your maple init file. In Maple Help, see worksheet,reference,initialization. Or go to the URL http://www.maplesoft.com/support/help/Maple/view.aspx?path=worksheet/reference/initialization .
This is written here http://digitalcommons.usu.edu/dg_downloads/5/