HCO is not a compound, it is H₂CO
In this structure, we draw two Hydrogen atoms to the left of Carbon, one above the other. Then we connect them to Carbon with single lines, showing their bonds.
Next, we draw the Oxygen atom to the right of Carbon and join the two atoms using a double line, showing their double bond.
Finally, we add two pairs of two dots to the Oxygen atom, showing its two lone pairs.