Thought I would chime in on this thread. Gnome Sequencer needs to be added to your WoW addon directory. However it does not have an addon access button to manipulate the addon from within WoW. You need to follow the installation directions that tell you rename a file (exampleSequences.lua) to Sequences.lua.
In the Sequences.lua file you add the macro sequences you want. There are several GS compatible files out there (See
http://wowlazymacros.com/). Then you add a macro that references one of the sub-sequences in your Sequences.lua file. For example if you had a sequence that starts
Sequences['Attack'] you would create a macro that contains
/cast Attack in it. Then when you use the macro it will execute the commands in the Sequences.lua file.