In prior Sextante-version the "run-button" could be found in Graphical Model Interface:
The behaviour of executing models has changed. Currently model path must be saved on disk space (like e.g. C:\model\test.model)
After that step user will have to define the model directory in Sextante settings:
At the same time a new node will be placed in the parent tree of Sextante toolbox, where models will be listed.
The model can be executed by right-clicking with the mouse on the model entry and activating "run".
Have fun with creating models in gvSIG CE!