Sit side by side with the child on the floor. You should both be viewing the lesson from the same perspective. If the child is too distracted on the floor, you can use a table, but generally knobless cylinders are worked on the floor because the height of the towers is too high for a table. You are not building towers for this exercise, however, so either location will be okay.
Select a comparison to make. WIth knobless cylinders you can use vocabularly like "large and small," "thick and thin" or "tall and short." You an use any of these sets of words, but you should only introduce one at a time. For this example, we will use tall and short.
Pick out a tall cylinder and a short cylinder from the fourth set of cylinders. As the child becomes more comfortable with the vocabulary, you can use other sets, but at first you should use a set of cylinders in which tall and short is the only variable.
Present the cylinders to the child. First place the tall cylinder in front of the child, saying, "This is tall...tall...tall." Continue to touch the tall cylinder as you repeat the word. The child may begin to repeat the word along with you, but is not required to do so. The same thing is done with the short cylinder next, but you will say, "This is short...short...short."
Ask the child to distinguish between the cylinders. You might say, "Can you touch the tall cylinder? How about the short one? Now touch the short one again." You can rearrange them as you do this to encourage the child to distinguish between the sizes rather than the locations of the cylinders.
Reverse the process to help the child recall the names. You can place both cylinders in front of the child, then point to them asking, "Which one is this? How about this one?" This will help her retain the vocabularly as well as being able to identify the objects when presented with the description. This can be done over and over with various cylinders as long as the distinctions are clear. As the child becomes more comfortable, you can make the sizes closer and closer together.