In the Free Edition, you will be prompted to upgrade if you use a feature that requires an upgrade, such as entering a 1099-MISC or itemized deductions. You can manually upgrade to Deluxe by using the Upgrade button on the left side menu. See image attached.
If you don't have an upgrade button, verify that you are using Free Edition. If you are using Free File, you won't be able to upgrade. Free File is an IRS alliance program and does not allow upgrades. You either qualify or you don't. If you don't qualify, create a new account and start out in Deluxe. Use this link - https://turbotax.intuit.com/personal-taxes/compare/online/