Indeed, rwg is correct. HE.Net gives you 2 /64 blocks, one is used as the point-to-point address for the tunnel itself (referred to on the tunnel details page as the "Server IPv6 Address" and the "Client IPv6 Address"). The other is your block to be used on your LAN (referred to on the tunnel details page as the "Routed /64").
The correct configuration is:
interface Tunnel1001
description My Tunnel (Hurricane Electric)
no ip address
ip virtual-reassembly max-reassemblies 64
ipv6 address 2001:470:xxxx:xxxx::2/64 (This is the "Client IPv6 Address")
ipv6 enable
ipv6 virtual-reassembly
tunnel source GigabitEthernet0/0
tunnel mode ipv6ip
tunnel destination xxx.xxx.xxx.xxx (This is the "Server IPv4 Address")
interface GigabitEthernet0/0
description My WAN
ip address xxx.xxx.xxx.xxx (This is the "Client IPv4 Address")
interface GigabitEthernet0/1
description My LAN
ip address xxx.xxx.xxx.xxx (This is your internal IPv4 address for your LAN)
ipv6 address 2001:470:xxxx:xxxx::1/64 (This is the "Routed /64 Address", host :1)
ipv6 route ::/0 Tunnel1001 (Send all IPv6 traffic through the tunnel)
Note that I've left out some configuration items, like NAT for IPv4, access lists, CBAC/Firewall, and IPS.