How do you do it? I used to be able to explain it well but ever since I “lapsed” and barely go to Mass right now, I can’t find an explanation. My DH had been a JW for most of his life and recently he decided he is Catholic again but now I don’t know how to help him understand that part of our faith. He was a JW since 8 yrs old but was a fully initiated Catholic because his dad was Catholic while mom switched to JW and now she’s a Catholic again. After praying to St Monica for several yrs he finally said he considers himself Catholic, has actually gone to Mass and pushes for us to go but I am the one who makes up excuses to not go… so because of this I have forgotten how to explain things and I used to be a Catechist… sigh!
Respectfully, a suggestion - as you yourself are a self-described lapsed Catholic, it is probably most important for you at this time to focus on restoring your own faith and spirituality. Once you have done so, in Christian fashion, your example of life in faith should be evident to those close to you, and will provide opportunities for you to discuss such theological and other matters with confidence and strength of faith.
Trinitarian theology is tough for many to understand completely, and still provides ample opportunity for debate among Apostolic Christians (see the hundreds, if not thousands of threads here and elsewhere on the Filioque). The simplest way is to start with the Creed and prayerful expressions from the Mass and Divine Liturgy. These reflections and meditations might prove useful to you in restoring your own faith.
For example, in the Byzantine Divine Liturgy, one of the responses is a reflection on the Trinity.
Deacon (or Priest): Let us love one another that with one mind we may profess.
Response: The + Father and the Son and the Holy Spirit, the Trinity one is essence, and undivided!
Three Divine Persons in One God