A steward is a person who manages property for the owner. In this case, the steward is us souls and the owner is God.
Everything belongs to God
All experiences and qualities in life ultimately belong to God (the One Creator). For example, a person might have an amazing memory. This soul has been given this gift, this quality of life, and is thus a temporary steward of its experience. The quality - a good memory - is owned by God, its creator, and it is being displayed to the world via the medium of the embodied soul that has been given the gift. Its appearance and expression - via the embodied soul - is entirely due to the Creator of all - God. As a steward, the soul does have the freewill to ignore or improve the quality. This is true for everything else in life, we - the souls - have freewill that is yet another created quality. There is nothing in life, this world, and all universes that is not created by God.
Everything in life is like this. Another example is that of a person with a beautiful face. The soul can choose to accept this quality with thanksgiving and happily display their beautiful face, or they can try to hide it or make it ugly. We have the freewill to do what we like with all we have been given. The enlightened soul realises this and decides to display, enhance, or improve all the things that God has given them and to be able to share all their good qualities and experiences with others who will appreciate the gift them. This involves the realisation of wise sharing. It is not wise to attempt to share our good qualities and gifts with those who will not understand or appreciate that which we are doing. It is the experience and advice of the wise to only share with other like minded and indeed spiritually minded souls - souls who understand and appreciate that which you are sharing. Ignorant souls are highly likely to abuse our kindness and good will and to use our sharing for their own ignorant and selfish desires.
Spiritual stewardship involves identifying, acknowledging, appreciating, and thanking Life/God for all the good qualities and experiences that are given to us by God/Life. God is the Creator of all things, all souls, all worlds, all embodied and disembodied experiences, all Universes, and all creatures great and small. These are all expressions of God's Creative Abilities. The spiritually enlightened soul realises this, accepting, embracing, and nurturing all good qualities so as to be able to express and display them for the benefit of all.