Start smaller and practice.
It's hard to tell you how to overcome obstacles without knowing the obstacles. What are you trying to accomplish by reading other people's code? Then, what specifically do you find difficult in the reading that prevents you from accomplishing your objective?
If you're reading other people's code to learn to program or to be be a better programmer, you may be doing the wrong thing. First, there's no guarantee that some random code you find on the Internet is worth using as an example of how to do anything, and second, the best way to become a better programmer is to write code. There are books that dig into the specifics of the language and "reveal" some of the under the hood elements that once knowing might make you a better programmer. "Effective Java," is one of those books.
If I haven't guessed your purpose, then please come back with more detail.