There are 3 ways, tethering a smartphone, using a cellular mobile hotspot (mifi), and using a cellular air card.
Tethering usually requires a surcharge from the cellular provider, but can usually be turned on and off monthly and sometimes can be used for less than a month and you only pay pro-rated fee for that month.
There are ways around paying for the tethering charge, rooting or jail breaking the phone and running a tethering app.
My brother has a rooted android phone and we used his phone to connect our iPads to the Internet Thursday while we were at a golf tournament.
The other 2 options require buying hardware and paying a monthly fee.
I would call up some cellular providers in your area and see if they rent the mifi or air cards if you can't tether to a smartphone.