Select your input file - you may chose between different sources like iCloud, gallery or iTunes Library.
Some conversions are done on a secure cloud server so you must have an internet connection to use this app.
There you may also repeat sharing of converted files or delete those you don't need anymore.
Access your conversion history - there is a related tab in the app.
You should be aware that by using this app, you agree that your files will be sent over the internet from the app to the cloud server for conversion.