These type of puzzles are known as charade. What you have to do is find two words that are referred to in the first stanza and the second stanza and put them together to form the third word in the third stanza.
Just for an example, if my first refers to 'off' and my second refers to 'ice', then my whole will be office.
My first is present - future's past -
A time in which your lot is cast.
My second is my first of space
Defining people's present place.
My whole describes a lack of site -
A place without length, breadth, or height.
The two words hinted are:
NOW (The present time)
HERE (The present place)
Combining them, we get NOWHERE (A lack of place).