Easy: go to the sprite with the block. Drag the block and drop it on the stage sprite in the sprite selector area. Go to the stage. You should see it and be able to run it in the tell block.
If you grab an OF block from the Sensing category, set the right input to sprite S, then pull down the pulldown in the left input, you'll see S's local blocks. Then you put the OF in a RUN or LAUNCH block.
Yeah, OF is the official Jens-approved way to refer to another sprite's local procedure. The indented visual presentation of those blocks is meant to remind you that the block by itself has no meaning -- you can't drag it out of the OF block to put in a script -- but when paired with the sprite to which it belongs, it becomes something you can call/run in a script.