Can someone please tell me how to enter Dalaran for the first time? :-)

easiest way to enter dalaran is to get a mage to port u there or a warlock to summon you.

any level make it ur hearth and ur set to go

Or have some one in Dalaran that your partied with enter you into a Battle Ground.  When the battle grounds over you'll be in Dalaran.

I think there is a level 74-ish quest that sends you there, but don't quote me on that. Also, at level 77 you can learn Cold Weather Flying (Alliance trainer in Sholazar, don't know about Horde) and use your mount to fly there.

I got a mage in SW to port me there for 5g.

easiest way to pay for port or have a guildie port u there....otherwise walk to crystalsong forest and find the protected bubble in the ruins where you can click on the floating rune to translocate into city