I was "filled with the Holy Spirit" 34 years ago. As I continued to seek for the "baptism with the Holy Spirit," 6 months later the Lord spoke these words to me:
"My son, I filled you with the gift of the Holy Spirit 6 months ago. The gift of tongues is a gift I desire all my children to have whom I have filled with the Holy Spirit. The gift is yours if you in faith choose to partake of this gift."
So in faith I opened my mouth and began speaking tongues as the Spirit gave utterance. As I exercised more and more praying in the Spirit in my prayer language, I realized I could pray in tongues "anytime" I chose.
Prophesying in tongues with interpretation is "not" something you can do anytime you wish, but it is a gifting that becomes better through exercise as you learn to separate your prayer language from the anointing tongues/interpretation gift of the Holy Spirit.
You do not need to do any of this to be saved, but it sure helps you along the journey into eternity with Jesus.
Blessings