I wasn't replying to the question. I was replying to this:
So I guess we can all agree that absolute truth can be known, but whether we have it or not cannot be known at this time until it is revealed by God.
That's self-refuting.
As to the "how" question, first, you have to start with the assumption that it can be known at that it is, in fact, known. You cannot approach the question from the perspective that the absence of any coherent answer suggests that knowledge of absolute truth is impossible. Once you have the proper perspective (which means you rightly dismiss any self-refuting claims that you can't know), you go about the work of building an appropriate epistemology.
There is no short answer to your question. The reason is that "knowledge" is not a science with a universal method. It is the result of the particular object or problem to which it is addressed. Some objects or problems admit absolute certainty. Others do not. So I am absolutely certain that all triangles have three sides (a geometrical problem), that 1+1=2 (a mathematical problem), that God exists (a philosophical problem), that absolute truth can be known (another philosophical problem), that if A is larger than B and B is larger than C that A is larger than C (a logical problem), etc. I am not absolutely certain that the sun rises in the east (a scientific problem), but I absolutely certain that I am absolutely warranted in holding to that belief--that is, that the belief is justified--and further than any and all claims to the contrary are absolutely unwarranted. Likewise, I am not absolutely certain that George Washington was the first POTUS or that Jesus rose from the dead (both historical problems), but, again, I am absolutely certain that both claims are strongly warranted and that contrary claims are unwarranted. We can press further and note that I am absolutely certain of the validity of my sense-judgements, although I may question the inferences I draw from any of them, as it is all too common to have an unwarranted distributed middle in any given case.
What all this means is that you've asked the wrong question. You can't ask "how can we know if we have absolute truth" anymore than you can ask, "what does it weigh?" If I asked the latter, you say, "Uhm, how much does
what weigh?" Just so, we must know what we are talking about to know whether or not we have absolute truth about it.