upload your app.plist to dropbox
get shared link of app.plist, like https://www.dropbox.com/s/qgknrfngaxazm38/app.plist
replace www.dropbox.com with dl.dropboxusercontent.com in the link, likehttps://dl.dropboxusercontent.com/s/qgknrfngaxazm38/app.plist
write your download.html like INSTALL!!
upload the download.html to dropbox
get shared link of download.html, like https://www.dropbox.com/s/gnoctp7n9g0l3hx/download.html
replace www.dropbox.com with dl.dropboxusercontent.com in the second link as well, likehttps://dl.dropboxusercontent.com/s/gnoctp7n9g0l3hx/download.html
Now, visit https://dl.dropboxusercontent.com/s/gnoctp7n9g0l3hx/download.html in your device, you can install the app like before.
WHAT A WONDERFUL WORLD！