Step 1 - After downloading install Kingo Root on a Windows computer. Then plug your Samsung Galaxy j7 using the cable.
Step 2 - The program identifies and scans your device. You may have to activate USB debugging if asked by the tool. The interface will show a Root button. You should click it only after reading the instructions.
Step 3 - The rooting gets over in a short while. After that you have to click the Finish button to reboot the phone.