Moved - from Inst-Tech

@inst-tech YES. open the Arduino IDE, select Preferences, enter that path. 

Now download the ZIPPED github library.

Now in the Arduino IDE select Sketch>Include Library>Add .ZIP Library... and navigate to the ZIP file you just downloaded. Select it and it will be installed in your correct location. Check by looking IN THE IDE for a sample under File>Examples Have fun

For FUTURE reference if it's a known library to Arduino (I will pick one at random) use the Tools>Manage Libraries interface, just enter a search argument like 'GSM', now just wait for the pane to be populated. Scroll down the list looking for your best match. Normally the device or sketch you are using to start the particular project will recommend a library. If you guess wrong, don't worry, just try another one, the wrong guess is only occupying a few bytes of HDD space.

If you select the More Info for any core library this is where you end up. You can of course browse this huge repositry by web browser but it's probably quicker to use the Library Manager.

https://www.arduino.cc/en/Reference/Ethernet

Start here to see if this helps your education https://www.arduino.cc/reference/en/libraries/ (the instruction is wrong, it's not import library, it's include library)

This picture shows what happens with a blank sketch, then menu Sketch>Include library>WiFi. The blank sketch got re-written with all those include statements. Notice the greyed out headers. Use the IDR, do NOT mess about in the File Manager.

Good luck.