How do you draw a chair conformation from a fischer projection?
I will explain it on D-glucose.
The most important thing to draw the correct conformation of a sugar, D-glucose, is to pay attention to the stereochemistry from C-2 to C-5, because any change in the configuration of these stereogenic centers changes the identity of the sugar D-glucose.
At first we need to change the hydroxyl group on C-5 in the proper orientation.
To draw the chair conformation of D-glucose you need to know the orientations of the axial and equatorial bonds on carbon atoms of the chair conformation.
Below you can see how to determine what goes up and what goes down on the ring.
The final result: a chair conformation of D- glucose with equatorial and axial bonds.