Step 1: Find valence e- for all atoms. Add them together.

O:6
Cl:7x2=14

Total=20

Step2: Find octet e- for each atom and add them together.

C:8
O:8x2=16

Total=24

Step3: Gives you bonding e-. Subtract step 1 total from step 2

24-20=4e-

Step 4: Find number of bonds by diving the number in step 3 by 2(because each bond is made of 2 e-)

4e-/2= 2 bond pairs

Step 5: Find the number of nonbonding (lone pairs) e-. Subtract step 3 number from step 1.

20-4= 16e-=8 lone pairs

Use information from step 4 and 5 to draw the lewis structure.

Lewis dot structure of OCl₂

Alternatively a dot method can be used to draw the lewis structure.
Calculate the total valence electrons in the molecule.
O:6
Cl:7x2=14

Total=20

Put oxygen in center and arrange chlorine atoms on the sides.Arrange electrons until both atoms get 8 electrons.