1. Make the content to be published :

LabelMoleculeDrawing[image_]:=MoleculePlot[MoleculeRecognize[image],<|"Carbonyl"->Bond[{"C","O"},"Double"],"Ring carbons"->Atom["C","RingAtomQ"->True]|>]

LabelMoleculeDrawing[]

2. Use the CloudDeploy function to publish to the cloud :

CloudDeploy[FormFunction[{"molecule"->"Image"},LabelMoleculeDrawing[#image]&,"JPEG",AppearanceRules->{"Title"->"Molecule recognizer"}],Permissions->"Public"]