i have the files downloaded on my computer and i use BBSAK to install everything. It says the theme or app has been successfully installed but it does not appear on my device
Try looking in various folders for the app. Depending on what folder you have your downloads set to go too, it they could be anywhere. I suggest forst looking in the Download folder. If they are not there, then go to your home page and press the BB button and then from the dropdown menu press Options. You should see a selection for "Download Folder". Open it and see where your downloads go. If the app is not there, then look where you may have had it saved in the past.
