You use it as a conjunction. It is classified as an "opposition subordinating conjunction" which means that it establishes an influence contrary to the main clause. This is similar to the preposition "despite."
"He won the race even though the other riders conspired against him."
Even though I am smart, I do not know everything.
He had had enough of their constant complaints, so he decided to speak up and clear the air.
He spoke tolerantly with her even though she cheated on him.
Even though I had already eaten, I couldn't resist the offer of a piece of cake.
Example sentence - He purchased the table saw even though it was non-returnable.
Robots are cool. There I used it in a sentence, even though I don't think robots are cool.
Example sentence - It is quite feasible for it to rain today even though rain is not in the forecast.
No: "Is this sentence correct even though it's not that fascinating?"
The advert was a great success, even though the model was commercially altered. (The advert was great even though the model was airbrushed)
even though he was 15, he still looked like a midget.
He was still voted as President of the school's Student Council, even though he acts immature and foolish.
Even though I love you, we can never marry.