The very first thing is you have to get a network cable. There you have mainly three options. They are Cat 5, Cat 5E, Cat 6. I recommend Cat 5E. The difference between Cat 5 and Cat 5E cables will give you a chance to choose Cat 5E. The unit prize of Cat 5E and Cat 6 will again give you a hint to choose Cat 5E. Always think about your target and try to achieve it in simple, efficient and effective way.
There are again several categories of Cat 5E cable. I used Cat 5E UTP cable.
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That's it. Now you have to connect the cable to the computers.