Making Cat5 Ethernet cables or repairing the ends is quite easy.
You will need a RJ45 connector, a crimper, and some strippers or a knife to strip the shield.
- Strip the outer shield while taking care to not harm the wires.
 - Straighten all wires and untangle them.
 - Put the wires in the correct order, O, OW, GW, Blue, BlueW, G, BrnW, Brn.
 - Insert them into the connector with the tab facing down.
 - Check that the wires are in the correct order and fully into the connector.
 - Crimp!
 - Profit!
 
