You can add a network interface to a virtual machine deployed on PureApplication System from the virtual machines view:

However, this step only configures the new interface at the hypervisor. You must also configure the interface within the virtual machine. This step differs depending on the operating system. For RedHat, see my other post on adding network interfaces to a RedHat virtual machine. For AIX, you would perform steps like the following to discover (cfgmgr) and configure (chdev) the new interface:

# lsdev
. . .
en0        Available       Standard Ethernet Network Interface
en1        Available       Standard Ethernet Network Interface
. . .
# cfgmgr
# lsdev
. . .
en0        Available       Standard Ethernet Network Interface
en1        Available       Standard Ethernet Network Interface
en2        Defined         Standard Ethernet Network Interface
. . .
# chdev -P -l en2 -a mtu_bypass=on      # Enable largesend
en2 changed
# chdev -l en2 -a netaddr=172.20.202.2 -a netmask=255.255.248.0 -a state=up
en2 changed
# ifconfig -a
en0: flags=1e084863,4c0<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,CHECKSUM_OFFLOAD(ACTIVE),LARGESEND,CHAIN>
        inet6 fd8c:215d:178e:1234:b1ec:97ff:fe24:e66f/64
        inet6 fe80::a8ab:50ff:fef4:cc04/64
         tcp_sendspace 262144 tcp_recvspace 262144 rfc1323 1
en1: flags=1e084863,4c0<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,CHECKSUM_OFFLOAD(ACTIVE),LARGESEND,CHAIN>
        inet 172.20.202.243 netmask 0xfffff800 broadcast 172.20.207.255
         tcp_sendspace 262144 tcp_recvspace 262144 rfc1323 1
en2: flags=1e084863,4c0<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,CHECKSUM_OFFLOAD(ACTIVE),LARGESEND,CHAIN>
        inet 172.20.202.2 netmask 0xfffff800 broadcast 172.20.207.255
         tcp_sendspace 262144 tcp_recvspace 262144 rfc1323 1
lo0: flags=e08084b,c0<UP,BROADCAST,LOOPBACK,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,LARGESEND,CHAIN>
        inet 127.0.0.1 netmask 0xff000000 broadcast 127.255.255.255
        inet6 ::1%1/128
         tcp_sendspace 131072 tcp_recvspace 131072 rfc1323 1
#

This configuration will persist across reboot. You could also use the interactive smitty tool to configure the interface after you have discovered it.