Both options are managed via the OPTIONS / SIZES tab when editing a product.
When viewing the product list screen in the CMS, each product with a product variation will have a variant count shortcut visible on the product. Clicking this will take you quickly to the Options / Sizes area.
You can also navigate to Options / Sizes area via the Options/Sizes tab at the top of the edit product screen or the Manage Options button at the base of the description area.
Once on the product variation screen your existing variations will be listed. You can edit the values, add new ones or delete via the red X icon as indicated.
You can edit more complex values for each variation, such as dimensions, trade pricing etc. by using the green pencil button next to each variant.
Product options that are not configured using the Product Variations option, can be edited via the Options/Sizes then Colours, Sizes, Options/Styles and Custom Questions buttons.
Select which tab you require, then use the delete button next to the simple product option you wish to delete.