"The rope is one uja long."
Translation:wa' 'uj'a' 'ab tlhegh.
There's no way to add that to this sentence. There's three basic ways to use 'oH.
You could use it as the subject: wa' 'uj'a' 'ab 'oH ("it is one uja long"), but this sentence instead specifically states that the subject is tlhegh so you can't use it there.
You could use it as the object: 'oH 'ab tlhegh ("The rope is it long"), which is very odd, but I suppose if we had already been talking about a particular length, a sentence like this could be used.
The third way to use it is in an equational copula. If the rope were stuck to something to indicate the length of something else we might say something like, wa' 'uj'a' 'oH tlhegh'e' ("The rope IS one uja"). This is not necessarily saying how long it is, but saying that it is the same thing as one uja, as if we are not talking about the measurement of the rope, but rather how it is being used.
Do not get in the habit of thinking that the word "is" always needs to be translated by using a pronoun as "to be". Many Klingon verbs include "be" as part of their definition and just take the noun as the subject without using a pronoun. The official definition of 'ab is "have a length of", So the sentence at the top of this discussion could be translated "The rope has a length of one uja." You could also translate 'ab as "to be ___ long", but when you use it that way, "be" is included in the word 'ab and does not need to be added in to act as a verb.
Now that I have more time to study your response, I think what I meant was, "wa' 'uj'a' 'oH thlegh'e'." That is, to emphasize the ROPE. Now I can see that it looks like the rope is literally "1'uj'a'." ...Now if I want to emphasize rope, or one, or uja; I could use "tlhegh'e', or wa''e', or "'uj'a''e'; correct?