The answer that I am about to give assumes the following:
a) That you are already a Christian, someone indwelt by the Holy Spirit
b) That you have a heart ready to obey God's Word
c) That you have a default principle of understanding the Bible plainly and normally
The best way to understand the Bible is to READ it. Read it again and again and again. Acquaint yourself with its contents. Be familiar with it. Familiarize yourself with the territory, so to speak. Get to know it like a friend. Let it be your companion. Hang out with the Bible often. In the process of time, layer upon layer, it will open itself up to you.
One portion here is explained in another. The Bible best explains itself. And all this require time and effort on your part to read it.
