The Ramchal, in short, teaches (Derech HaShem) that HaShem is absolutely, completely and perfectly good; His essence/nature so to speak is the totality of goodness. Because of this He wanted to bestow the greatest good possible. Anything less would simply not be good enough (the greatest good). But what is the greatest good? What is the ultimate good that God can bestow on His creation? The ultimate good is HaShem Himself. The greatest good that He can bestow is Himself.
So here's my question: HaShem can't give Himself literally: like when I give something to the other in order to receive it and becoming the owner of it. So how do I need to understand this, what's the meaning of HaShem wanted to bestow Himself (the greatest good possible) and how does one receive if it's not literally?