Probably the black stripe which was over the CPU capacitors and the black square sticker which was over the GPU capacitors are no longer adhesive. Each time one changes the thermal paste it is always better to substitute them but you could clean these stickers and apply them instead of new thermal tape if they manage to stick firmly. Up to you

Take the polyimide tape and cut it in pieces that would fit the areas in which the capacitors are. Lay these pieces of tape over the capacitors. Then, using a spudger, gently press the tape down and squeeze out the air which is among the tape, the processor and the capacitors.

If you have touched the metal surfaces of the processors with your fingers while you were applying the tape, clean them again with the ArctiClean #2 because the substances produced by our skin could weaken the thermal compound.

Finally put the fan and the heatsink together and apply a momentary stripe of tape over the edge they have in common in order to keep them together while you will be mounting them.