We are filled with the Holy Spirit by faith; then we can experience the abundant and fruitful life which Christ promised to each Christian.
First, you must sincerely desire for God to fill you with Himself, which really means you must want God to totally have His way in your life. Because God is total love and total wisdom and He always has our best interest in mind, we all should want that. Anything else is irrational. Therefore, present every area of your life to God.
Second, confess to God any known sin in your life and by faith thank Him that He has forgiven your sins -- past present and future -- because Christ died for you. By faith claim His promise of forgiveness and cleansing according to 1 John 1:9.
Third, ask God to fill you with His Spirit. In a moment I will suggest a prayer. But remember, from Ephesians 5:18 we already know that it is His will for you. And we know that in 1 John 5:14-15, it says, " This is the confidence we have in approaching God: that if we ask anything according to his will, he hears us. And if we know that he hears us–whatever we ask–we know that we have what we asked of him." I repeat: it says, "…we know that we have (present tense) what we asked of him."
Fourth, remember that we always receive from God by faith, so receive this gift by faith, as an act of your will, and thank and praise God for answering your prayer and filling you with His Spirit.