H has 1 valence electron

O has 6 valence electrons

Cl has 7 valence electrons 

Oxygen shares 1 electron with H to form O-H bond and another electron with Cl to form O-Cl bond.

Thus  Oxygen would be left with two lone pairs of electron on it, While Cl would be left with 3 pairs of electrons.

So the final structure would be       ..      ..

                                             H  - O  -  Cl :

                                                   ..      ..

The dots over O and Cl shows the lone pair of electrons.