Hello friend, God bless you, we can know the presence of God when we admire his creation, we can know it through his word, we can know the presence of God when we accept his son Jesus Christ as Lord and Savior.
Understanding his word is not difficult, you just have to read the Bible and ask the Holy Spirit to give you wisdom and understanding to be able to understand what God has written, everything that I have named makes you relate to God and it is what God wants of each human being that one relates to him, that they take him into account at all times. And that is how one can know his presence, even so, it is something that cannot be exactly explained with words, it is something very personal and a unique feeling.