Hi - if you add a Rigid Transform block to a line, you can create a new frame that is translated and/or rotated relative to your existing frames. Typically, you would connect the B port to the starting frame, set parameters to define the rotational and translational transformations you wish to apply to the existing frame, and the new frame that lines up with what you need will be available at the F port of the Rigid Transform block.
If you look at the shipping examples, these blocks are used in nearly every example. Run >>sm_four_bar, go into the Mechanics Explorer, and click on one of the Rigid Transform entries in the tree view on the left hand side. You will see the 'B' and 'F' frames highlighed in the 3D view. If you compare those to the transformation defined in the Rigid Transform block, you will see how to use that block.