(Optional) Run the script proccess_wipsvg.sh. (It generates the proper pngs and move the svg from wip to depot folder.)
Breaf instructions: A template file contains three layers (to see them, select Layer - Layers from the menu; to toggle layer visibility, use the eye-like icons near the layer names). The bottom layer contains the background of the icon. It has proper color, shadow, shade and tint. Do not modify those.
The top layer (hints) shows the keyline shapes, the regions that define the size of your icon. In short, a mostly square icon must fit into a square one (black lines). A horizontal rectangle, in the horizontal rectangle (blue lines). A vertical rectangle icon, into the vertical rectangle (green lines) and the mostly round one should mostly fit in the larger square-without-the-corners that they form. Most part of your icon should fit into one or several of those rectangles. Note that small items can extend beyond this area. For more information on this, please refer to the section "Proportions" below and to the Google's guide.
The icon layer is the most interesting one. This is the layer you should draw your icon on. It already contains an indication, please delete it and draw the desired logo in white (#ffffffff) instead of it.
Add Activities to appfilter.xml
You can use Turtle to obtain the code. Note Turtl sets the iconname as a string (related to the activityname). You have to change the string inside: drawable="xxxxxxxxxx" /> and make sure it is identical to the .svg you put into the svgs/wip folder.
Please read this carefully for a deeper understanding: