If you have a previous version of Soil Samples V8 installed you must uninstall it from your Android's "Settings" area. Go to Settings, then select Apps, find SoilSamplesV8, and Uninstall it.

Then you must exit to your app icons and find the "My Files" icon and open it. Select Internal storage, then Android, then Data, then com.outfarming.soilsamplesV8. Press the folder icon in front and delete the folder by pressing the garbage can icon. Then exit back to your main icon screen and download and install the new app from here.