I started teaching yoga this year and am wondering where I deduct the costs for training, along with supplies like yoga clothes

If you are teaching yoga with an intent to make a profit, you will report your expenses on Schedule C.  

Your initial Yoga Teacher Training costs will not be deductible per the IRS rules. It isn't qualifying work-related education if it is part of a program of study that will qualify you for a new trade or business. See IRS Pub 970 for more information: https://www.irs.gov/publications/p970/ch12.html  Additional training hours, could be deducted if it maintains or improves skills needed in your present work.  Your clothing for teaching yoga will not be deductible per the IRS guidelines, as they can be worn for other activities. Your yoga mat, and any props that you may have purchased would be able to be included in your deductions. There are other possible deductions that you could qualify to use, please see the following TurboTax link for more information:  https://turbotax.intuit.com/tax-tools/tax-tips/Self-Employment-Taxes/Reporting-Self-Employment-Business-Income-and-Deductions/INF12031.html

For instructions on how to report your expenses on your return, please see the following TurboTax FAQ:

https://ttlc.intuit.com/replies/4800425