“Pivot section”: the master, the model layout which you want to copy or replicate. You lay out the board layout of one hierarchical sheet which works as the model for other sheets.
“Anchor module”: module means the same as footprint in KiCad. That’s an unfortunate name and AFAIK only “footprint” is used in KiCad nowadays. You decide which footprint is used as an “anchor”.
You position the corresponding anchor footprint of each hierarchical sheet where you want them to be, and the rest of the footprints are positioned relative to those anchors.
For example you have an IC U1 which has external capacitor C1. The same layout is repeated for U2/C2, U3/C3 etc. You can choose U1 as the anchor module. Position every U manually. Position C1 next to U1. You want to replicate the relative positioning of U1 and C1 to each other U/C pair. Select U1 which you have chosen to be the anchor footprint of the pivot section.
Open the plugin. Select the hierarchy level (in this case only one is available). Select sheets to replicate: you should see the list of the sheet names and the reference designators of the anchor footprints, in this case U[x] Test by selecting them all. Click OK. Now every U should be where you put them but every C should be moved automatically and placed next to their U, like in the pivot section.
The genius of the latest version of the plugin (well, I may be partial because I gave the ideas) is that you don’t have to declare or set any footprint or section. You just select one footprint, any footprint which belongs to any ready-made layout section which could be replicated, and open the plugin dialog. The only thing you have to remember is that the selected footprint and each corresponding footprint of other hierarchical sheet instances stay where they are. The footprints from the same sheet instance where the selected component is will stay where they are and are used as the “pivot section”, i.e. the model to be replicated.