Either way is just fine. The only thing you want to avoid is doubling the antenna wire back on itself. This will effectively shorten the antenna and reduce the range of the radio. But however way you want to route it out and up is fine. I will usually route mine out the bottom and along the bottom of the fuselage. Here are a couple of pictures that can help you out. Use a strain relief at the end of the antenna to keep it tight, and it protect your antenna wire if it gets snagged or bumped. I also like to have a strain relief on the inside of the fuselage where it exits the fuselage to keep the wire from being pulled out of the receiver. A good source for strain reliefs are servo control arms that are cut off.

Hope this helps

Ken