At salvation we are justified, after which we enter into the next phase of our walk where the process of sanctification begins. This is a continuous process as we mature in God. If a person did not get filled with the Holy Spirit after he or she got born again, they need to ask the Lord to fill them with the Holy Spirit. Tongues are a gift from God, an initial evidence of the baptism with the Holy Spirit. Praying in other tongues, allows you to pray the will of God by the empowering of the Holy Spirit. For if I pray in an [unknown] tongue, my spirit [by the Holy Spirit within me] prays, but my mind is unproductive [it bears no fruit and helps nobody]. 1 Corinthians 14:14 (AMPC)
When you pray in tongues, you are yielding to the Holy Spirit who now dwells in you. Then you are allowing that same Spirit to pray through you, so you are in tune with Him.
Yield to the Holy Spirit. If you are not yet filled with the Holy Ghost, you can ask the Lord right now to fill you. And start praying in tongues, pray every day and build yourself up in your most holy faith, as in Jude 1:20.