How to adjust the Internet for a subnet?

Question

I have 2 interfaces:

eth0 and tap0.

eth0 - external interface, tap0 ( 192.168.100.0/24 subnet ) - internal interface. How to add internet to internal interface ?

I execute:

echo "1" >> /proc/sys/net/ipv4/ip_forward

iptables -t nat -A POSTROUTING -s 192.168.100.0/24 -o eth0 -j MASQUERADE but ping www.com or ping ip not work in computer with ip 192.168.100.2