Fleetola is built to be used at the kerb. Everything you do at a desk you can do on a phone: write and sign a contract, take the handover photos, mark the damage, record a payment, end a rental.
In your phone's browser
Sign in at the same address you use on a computer, with the same email and password. On a small screen the sidebar becomes a bar along the bottom - Dashboard, Contracts, Money, Vehicles and More, which holds everything else - and every form opens as a sheet from the bottom of the screen. The search, the messages and the bell sit along the top.
The Fleetola app
The Fleetola app for iPhone and Android is the same Fleetola, with the same login and the same data, in an app. It adds two things the browser cannot: push notifications the moment something happens (see Alerts that come to you), downloads that open your phone's share sheet so a PDF can go straight to email or Files. The apps are on their way to the App Store and Google Play; until Fleetola is in your phone's store, the browser does everything except push.
When the app asks you to update, update it from your store. It only asks when the server has changed in a way an older version would get wrong, so the old version is stopped rather than left to save something incorrectly.
Signing out of a lost phone
Sign out everywhere under Settings → Your account ends your login on every phone and computer at once, including the one you no longer have.
Tip: Your renters do not need the app either: their portal works in any phone browser. See Set up the renter app & portal.