Apple does not allow apps to be installed from a website — only from the App Store. So on iPhone you use the website version. It is the same expense manager, in Kannada or English, and once you add it to your Home Screen it opens full screen, like an app.
Open this page in Safari (not Chrome), then tap the gold button above.
Tap the Share button — the square with an arrow, at the bottom of Safari.
Scroll down the list and tap Add to Home Screen.
Tap Add at the top right. The icon is now on your Home Screen.
Open it from that icon. There is no sign-in — you are straight in.
WHAT YOU GET
Record every expense in Kannada or English, with the same categories
The month view, the category totals and the reminders
Full backup: save a backup file, and restore it on another phone
WHAT IS ONLY ON ANDROID
Signing in with Google to keep a copy in your own Google Drive — on iPhone, save the backup file yourself instead
Your money stays yours. Nothing is sent anywhere — the entries live on that iPhone only. So don't clear your Safari website data, and save a backup file now and then.