You can study with ABA English however you feel comfortable, from your computer, your smartphone or your tablet.
If you have an Android device, you can download it from the Google Play Store.
If you have an iOS device, you can download it from the Apple store.
If you want to access the course using your computer just log in to your Campus.
Even if you study using several devices, your progress will always be synchronized, as you're using the same account. So you can start with your computer at home, continue on your smartphone during your lunch break for example and vice versa.
Remember that some sections are exclusive to the web version (Campus) and you will only be able to access them by going to campus.abaenglish.com.