How to create DHCP in a router so that I can share internet to my local network

Your router must support DHCP. Typically, most Small Office/Home Office routers that you purchase for about $40+ all support the use of DHCP. And the configuration is almost automatic out of the box.

Your PC's must all be set to acquire their IP addresses via DHCP as well.

Go to a command prompt and type IPCONFIG /ALL and hit Enter. Then go back up to where the IP address information is. Note the Gateway address. This will likely be 192.168.1.1. If this is the case then you should be able to get out to the Internet. Then look in the back of your router. Is there a 4-port switch built in? Connect your PC's here. If your, take your single LAN port and connect it to a small switch that you can purchase. THen connect your PC's to the new switch. Now that the connection is shared, they should all have access to the router and it should assign each PC a unique address from the DHCP server. ALong with the information it receives, it gets a Gateway address. This is the route that the PC will take to go to an IP address that is not located on your Home network. The Internet is not on your home network, so the router will route your requests out to the Internet.

You shouldn't have to do anything. All Broadband routers come with DHCP built in and turned on by default. As long as your PCs are set to automatically obtain an IP you will be fine.