Once precise location is enabled on your device, compose a Tweet as you normally would. If you haven't previously attached a location to your Tweets, you may see a prompt asking if you’d like to enable precise location.
Tap the location icon in the Tweet compose box to open a list of places that you can choose.
Select the location you want to add to your Tweet.
If you’re attaching a photo to your Tweet that was taken on the in-app camera and tap the location icon, your precise location (latitude and longitude) will be associated with the Tweet and findable via API.
For earlier versions of Twitter for iOS, your Tweet will always contain both your selected location name and the precise location of your device (which can be found via API) when you Tweet.
The next time you Tweet using the Twitter app on the same device, your general location will automatically be displayed with your Tweet, using your current location. For Twitter for iOS versions before 6.26, your precise location will automatically be attached to the Tweet (and findable through API) along with the general location.