Chaima55, you've no chance of making it at home.
Glutathione is a water soluble tripeptide ( a type of small protein molecule) made from amino acid residues. It is not an amino acid in itself despite what you may read. It occurs in every cell in your body and as an antioxidant, its principal uses (and selling points) are to scavenge free radicals knocking about in the body and rid the body of various toxins at a cellular level.
The link provided by perseverer is the biggest load of rubbish I've read for some time. The article discusses a "glowing" effect on the skin if the instructions are followed. I can't quite see how a glowing skin is analogous to the whitening effect you seek but there you go.
The list of vegetables in the article will certainly make your skin glow if you knock back enough of the blended juice. The carotenes in carrot will turn your skin orange if taken in excess. Similarly, the anthocyanins in beetroot and the other vegetables will have a similar but not as prominent effect. If you're looking for glutathione, the highest amounts are found in watermelon, garlic, avocado, onions, asparagus and most of the cabbage family. The list of vegetables in that article should be ignored and the claims made are ridiculous.
There is virtually no evidence to show that glutathione possesses any skin whitening properties despite what you may read on the Internet.