How can I create Skooma in Skyrim?

No, you can acquire all of its ingredients but cannot reproduce it.

You can, however, obtain it at the following locations:

• It is sold by most Khajiit caravans throughout Skyrim.
• Fort Dunstad Commander's quarters.
• Random NPC's sell it near Whiterun, Riften and Solitude. If you respond to the NPC by asking if it is illegal to sell skooma, he will attack you and you will be able to loot his skooma and other items (including Sleeping Tree Sap) once he is defeated.
• Unnamed bandit camp at a rock overhang NW of Whiterun, below Dragonsreach; follow the city wall or the foot path north towards Halted Stream Camp. About five bottles of Skooma in the shelf, as well as other provisions, ingredients, and a locked chest.
• Knifepoint Hollow. One bottle is on a table next to a flute.
• Three bottles on a barrel outside of Ustengrav.
• Enthir of The College of Winterhold sometimes sells skooma.
• M'aiq The Liar can be pickpocketed for 3 bottles of Skooma.
• Prisoners at Cidhna Mine can be bribed, brawled, or persuaded to give the Dragonborn skooma. The skooma can be traded with Borkul the Beast to have Madanach's cell unlocked.
• Cragslane Cavern has some Skooma and Moon Sugar.
• The NPCs in the quest "Skooma Trade" may have some on them.
• In Liar's Retreat, there are two bottles on the shelf behind the bar.
• In the Riften Warehouse there are bottles of skooma and moon sugar on the shelves. This location is part of the quest Skooma Trade and can only be entered at a certain point in the quest.
• Three bottles can be found in Septimus Signus's Outpost, in the cupboard. Taking them is considered a crime.

http://elderscrolls.wikia.com/wiki/Skooma_(Skyrim)

Someone made a Mod that adds skoooma crafting:

Realistic Skyrim Skooma

You can make it. You need Moon Sugar and Powdered Mammoth Tusk. You can get the powder from Imperial Wanderers. (As in Wanderers who are of the Imperial race, not people that are part of the Legion.)

Skooma can be found at the red water den

The woman at the desk sells it and 13 bottles of skooma And 13 bottles of red water den skooma along with moon sugar can be found there

Skooma can be fond or purchased throughout the world Such as riften warehouse. Cidnah mine . Red water den and it can also be made with moon suger and mammoth tusk powder