I see that you are working in TurboTax Premier, and I assume that your wife is either a sole proprietor or a single-member LLC, filing her business income and expenses on Schedule C.
The Schedule C is begun by entering income from the Form(s) 1099-MISC. Is the gallery reporting your wife's gross sales or only the net sales after deducting their commission?
If the gallery is reporting net, there is nothing else to do regarding income. If the gallery is reporting gross, your next step is to deduct the commission on sales on line 10 of Part II. Also in Part II, deduct supplies, office expenses, vehicle expense, insurance, studio rent and business licenses that your wife incurs in the "business" of being an artist.
In Part III Cost of Goods Sold, you will deduct the cost of canvases, paints, framing, etc. that actually become part of the finished works that your wife sells.
