Log in to your Website Admin Panel with your credentials.
You will be directed to the dashboard. Hover your mouse to left menu options and click Products then Products again..
Then select the product you would like to add a product attribute to (Like a size or colour choice) but selecting the edit button when hovering over it.
Then scroll down a little until you see the Product data area that has a range of options like (General, Inventory, Shipping, Linked Products etc.)
Then change simple product to Variable product.
Then set the SKU for the product
Next select the Attributes option
Then select the custom product attribute drop down area and select to add either the size or colour options or both.
Once these have been added select the size and or colour options that appear in the middle of the product data area.
Then enter the size or colour values in the following format:
S | M | L | XL | XXL
6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | 22 | 24
Then tick the visible on the product page and the used for variations options.
Then hit the save attributes button and then select the variations options on the left.
Once that is done select the Variations option on the left
Now select the Add Variation button in blue.
Then once the product variation expands enter a price in the regular price area.
Then select a default size and or colour
Once that is done please scroll right to the top of the page and hit the Publish button in blue on the right.
Your product should now be live on the website.