The pictures you posted earlier shows the lower ball joint clearly. I have circled it in red. To make things clearer for you, the round bottom part (upper in case of the upper ball joint since it is oriented opposite when fixed to car) has been circled in blue. Ball joints are pressed inside the trailing arm which has a round hole to accept the same.
Its a tight fit requiring a press to fit or extract. Also, one needs to have it correctly placed while pressing else disaster can strike (they can pop out or spin inside the hole). Therefore you need a mechanic who is well versed in VDubs to carry out the work under his supervision at the press shop. I warn you since you are spending good effort and money to source quality parts, do not skimp on choice of mechanic please.
Finally, the yellow lines show you where the dust boot was supposed to be on the ball joint in your car. I guess the absence of the same makes the ball joint look hardly like one!!
