To change your accounting method requires that you file IRS Form 3115 - Change in Accounting Method with your return. While the 3115 is included with the TurboTax program, this form is not simple by any stretch of the imagination. So if you don't "really" know what you are doing, seek professional help.
Note that for rental property, when you change from cash to accrual, this will be a real PITA when a tenant stops paying you rent for *ANY* reason. Additionally, file the 3115 now will *not* help with your 2019 taxes. If anything, it will hurt. Even tax professionals will tell you that reporting rental income on an accrual basis is a bad idea.
