The simple way, as mc73 said, is to copy the apk file into your device and then install it from there.
When you compile a project, a file is created with the extention .apk and saved automatically in the Objects folder in your PC. same folder that holds your b4a project.. you need to connect your phone, open a folder in your phone, such as Dounload folder, then copy the .apk file in that folder. Now disconnect the USB cable and go to Download folder (or any other folder where you copied the .apk file, and open it, then follow the installation instructions.
Hope this will help you.