How to wedge d/hash notation a molecule?
If not using a Fischer projection, structural formulae with hashes and wedges allow to be more specific.
In the structure drawn in your current question, you provide information about the connectivity of atoms within the molecule, up to a point to indicate if the bond between two atoms is a single, double, or (not present here) a triple / quadruple.
Using wedges and dashes, equally provides this information; however additionally informs the reader about the sterochemical relationship of the atoms bound around an atom in a centre, addressing a specific (R)/(S) configuration.  Returning to your example, there are three sterogenic centres that I marked by an asterisk:

and for each centre you may find a pair of either configuration; for example for the hydroxyl group in $\alpha$ position to carbonyl alone

In total (for 3 stereogenic centres), there are $2^3 = 8$ distinct stereoisomers possible with different properties, which all fit into the first &quot;line only&quot; general representation.