A little background story. I forgot to bring my laptop that have been registered to connect to the office network (through VPN). But, there's flaws in it, they used MAC address to register the person who wants to use the network, so I just need to borrow my friends laptop and change it to my MAC address.

Here's how I do it.

1. Get your MAC address

$ ifconfig
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
    options=400<CHANNEL_IO>
    ether XX:XX:XX:XX:XX:XX  <-- here
    inet 192.168.100.10 netmask 0xffffff00 broadcast 192.168.100.255
    nd6 options=201<PERFORMNUD,DAD>
    media: autoselect
    status: active

2. Turn down the interface of your PC/Laptop

Example of the interface name: wlp4s0

sudo ip link set dev <interface> down

3. Change the MAC Address

XX:XX:XX:XX:XX:XX --> is your MAC Address that you want to use.

sudo ip link set dev wlp4s0 address XX:XX:XX:XX:XX:XX

4. Turn up the interface again, with the new MAC Address

sudo ip link set dev wlp4s0 up

Boom you can connect to the network !!!