Yes you can do it yourself with a home-made contraption consisting of a long bolt, two huge washers and to heavy nuts. Kinda like a cheap press.
Since you probably dropped upwards of $100 on the headset though, dont get cheap on us now and possably ruin it. Just take it to the shop and pay the extra ten bucks to have the cups pressed in correctly.
Heck, if you bought the bike or hs there, they may just do it for free.