Initially, the virtual appliance uses DHCP to dynamically obtain an IP address during appliance startup. For clients on the Internet to connect to your Access Server virtual appliance, you will probably need to use a static IP address. See the information on the "How to change the IP address and other network settings of the Access Server appliance?" question of the FAQ.
You also need the the appliance's IP address to be reachable by clients on the Internet. Typically this involves either using a public IP address (e.g., an address provided by an Internet Service Provider), or configuring your Internet gateway/router to perform port forwarding. For the latter option, consult the instructions from your ISP or gateway/router on how to configure port forwarding.