The way it used to work is you install Dolphin Jetpack and then the legacy flash player from the play store. Recently, Dolphin included the jetpack in the new version. So you have to uninstall Jetpack, install the new Dolphin. However Adobe recently changed something and the legacy flash player doesn't work. There is a hacked apk that does work, I'm using it now. However I can't find the link, but just do a google search for 'dolphin flash apk" and search the last month, you should be able to find it.