You can easily reach Grenoble :

-by TGV train from Paris or Lyon (see SNCF web site)

-by plane via Lyon airport (code: LYS) and the bus shuttle to Grenoble.

-by plane via Geneva airport (code: GVA) and the bus shuttle to Grenoble.

-by plane via Grenoble airport (code: GNB, low-cost companies) and the bus shuttle to Grenoble.