For administrators wanting to install the extension for all users on a machine, you must unpack the .xpi contents into the SeaMonkey application directory's extensions folder.
If you have downloaded a specific version of the extension as an .xpi file (which is a standard ZIP format), you can simply drag and drop the file onto an open SeaMonkey window to initiate the installation. adblock plus seamonkey download
If ads are still appearing, you can manually update your filter lists by clicking the Adblock Plus icon in your toolbar (or status bar) and selecting "Filter Preferences" to refresh your subscriptions. For administrators wanting to install the extension for
The official SeaMonkey Release Notes explicitly recommend considering uBlock as a lighter, more modern alternative to Adblock Plus for the current browser engine. adblock plus seamonkey download