The other one is a VGA aka D-Sub 15 pin. You need a DVI (female) to VGA (male) adapter, don't get the sex backwards or you'll turn gay and also it won't work.
VGA is analog and somewhat undesirable but it will work alright enough if it's not an especially hi-res display. I'm 75% sure you can't use both the HDMI and DVI on that board at the same time but you could always try this
for $9 and prove me wrong. If so you'd have two digital connections.
Remind me again what res are those displays? I don't remember you saying you had two