What's the best way to remove or fade freckles? Does bio oil used for stretch marks and scars do anything for freckles?

Pigment. There are a few options for treating abnormal pigment depending on your skin type. Some may include bleaching creams like hydroquinone, light chemical or laser peels, or broad band light (bbl/ipl) treatments. It typically takes several treatments and several months for lightening to occur. A plastic surgeon or dermatologist can assess your skin for the best option.
Multiple options. If the spots are from sun damage you can use a bleaching cream like hydroquinone. Many of these are available over the counter that you could try, stronger forms are available by prescription. You could also get a chemical peel or light/laser treatments. If the spots are dark or irregular you should always have them checked by a doctor to make sure they aren't cancerous. Bio oil won't work.