For the Illustrator Mirrorme plugin, download the installer from Astute Graphics' website. Select the plugins you want to install. Will install to the listed locations for the various versions of the application. Run the Astute Graphics installer. Once you have installed the set then on startup of Illustrator a dialog appears and gives you the option to run as a trial (a generous couple of weeks) or to activate the plugin (or purchase). As of writing this, the plug-in is free (part of four freebies included in the set). Currently, they are on the Astute Manager 3.
You can find it in the tools panel after install. Select it and apply to a selected item or layer. You can also find the panel via the window and Astute Graphics.
The key thing it works on a path (s) or an entire layer. It needs something to work with. Select the tool and apply, as you move and rotate the axes of the tool, you will see the outline of the design change. Once you have finished and release then a panel will appear and click apply to selection (the selected paths) or go for the layer option which becomes active. Or cancel
Each and every time you apply it to the selection, the selected path will change and prompt you with the same question unless you go to the right side menu of the panel and select the preferences and turn off the annotations dialog and then you won't see it and you can modify the settings then just via the panel. You will see the result of the effect. The only part of the path you are work on is the active axis and that it indicated by two very small triangles and also if using in this mode, you will see the other axes slightly grayed out to make it clear which is the active area.
If used, you will see the axes remain and if you add to the active area of the effect then you will see that duplicated in all the other axes. If you try and add outside of the active then nothing will happen. Anything on the layer will be duplicated (within reason as there are some objects that are problematic but paths etc should be fine).
You can change whether it is active or not, or if you wish to remove the axes. You can also reposition the origin point by entering a value in the X and Y without having to do this interactively. You can change the angle of the active axes via the panel as well as interactively. You can also change the number of axes which defaults to 3. You can set it up to 72 max to create an intense design. Set it to 2, 4, etc for more interesting tiled effects especially if the angle is 0 or 90 etc
You can repeat apply the layer / selection option over and over to create every complex designs
You can double click the origin and origin X and Y will appear and angle and number of axes and you can then enter new values (why it is origin X and Y there but on the main panel it is X and Y baffles) Still the double click is useful (press return does not work) as it means you can tweak the settings quickly from the center
I would love it if was also an erase feature, everything outside of the axes being erased. Also better indicators or colors for the active axes.
The plug-in is from Astute Graphics, please check out their website for more information and demo set