Yes, that's true. Lyft Income is considered self-employment income and you have to complete a Schedule C which is found in Home & Business/Self-Employed versions. At the bottom, I'm linking to a recommended instruction that emphasizes Uber but would be appropriate for you. If you have any other details regarding this question, please feel free to post them in the comment section.
One thing Lyft drivers need to be aware of is that the 1099-K (and 1099-MISC) you receive shows the total amount that Lyft collected for your rides; it does not have their fees, commissions, safe rider fees or phone rental payments taken out. You need to deduct those as part of your business expenses along with the mileage you drove. If you didn't keep track of the mileage or the amounts Lyft withheld (commissions, etc.) look on the 2017 Tax Information link on the payments page of your Lyft driver account. There is a summary sheet linked at the bottom and it shows the fees they took out as well as the mileage for the trips (your mileage may actually be more as you drove around waiting for a hit)
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