Ultegra R8000 crank spacer
Shimano hollowtech comes in various sizes. The links you posted was for a mountain bike. Mountain bike crank spindles are for 73mm frames, so they need spaces for 68mm frames. 

Shimano road crank spindles are for 68mm frames. A BSA (normal British threaded) bottom bracket, doesn't need any spacers, you just thread the cups on and then put the cranks in. 

I suggest you watch a tutorial on how to put on a bb and crankset and make sure you follow the manufacturers torque and grease recommendations. When in doubt, get a local bike shop to fit it or take in some food and drink for them and ask them to have a quick look so double check your work. 

Also, Shimano have excellent online document on which have all of this information and more. I think your BB and crank should have come with instructions on all of this, unless they've stopped physically including.