"I am writing these things to you about those who are trying to lead you astray." NIV translation
John is letting us know another reason for this letter and that is to be a warning. He is making them and us aware that there are false teachers (antichrists) trying to mislead them and us.
"As for you, the anointing you received from him remains in you, and you do not need anyone to teach you. But as his anointing teaches you about all things and as that anointing is real, not counterfeit - just as it has taught you, remain in him." NIV translation
The anointing that John is talking about is the Holy Spirit and that is God living inside of the believer. God is the source of all knowledge and wisdom and it is that Spirit that can teach you about God. This website (or any other Bible study) can be used as a tool to help you to study but only the Holy Spirit can truly make you understand the ways of God.
"And now, dear children, continue in him, so that when he appears we may be confident and unashamed before him at his coming. If you know that he is righteous you know that everyone who does what is right has been born of him." NIV translation
John sums up the reason that we walk the talk and that is to please our Lord and Savior. When He comes back, we do not want to be ashamed of what we have done with the new life that He gave each of us. We can see who is children are by looking at their actions.