How to access the Library folder I am asking the same question from before by other people. My Macbook Air cannot connect to LAN internet. At the network preferences tab, it showed that my USB LAN has a self-assigned IP address and will not be able to connect to the internet. The network status showed 'CONNECTED' but below, it mentioned about the self-assigned IP address. What is it about?

I tried to look for a solution via google but I check my system preferences that my Macbook Air does not have this folder called 'library' where I could delete some of the un-used file or un-wanted file from my Mac. How can I solve this because I really need to use the internet when I have to pay the internet bill every month for my student residence. I have asked my friend from the residence but they also don't know how to deal with it.

Is my Mac is not the original Macbook that does not have such a folder?

I am just worried. I am sorry that I am not a tech-savvy person.
Your title does not seem to have anything to do with your actual question, you should change that.

There are a number of "Library" folders on your Mac, but the only one you should ever go into is actually hidden, meaning that Apple (for all intents and purposes) recommends you stay out of it. 

Why? Because deleting things in your users Library folder without knowing what these files do could cause more than a few things on your Mac to stop working.

If you just need to do some clean-up and delete unneeded files I recommend using a utility like Onyx (I use it, there are others that do similar things). And that will clean up the unneeded (cache and temporary) files for you, safely and easily.

If you want to go exploring though you can view  your Library folder by holding the Option key down while selecting the Finder's "Go" menu. "Library" will show up in the list and then all you have to do is select it to open a Finder window to explore.

But, again, be careful deleting things. If you do not know EXACTLY what a file is or does leave it alone or you could cause problems with your Mac, one or more of your Apps or numerous other things could stop working.