2003 Honda Accord Trunk lid tention bar

That's not something we commonly do, so you're going to have to look at how they work. Typically the bar clips in on one side and you give it a twist to engage it into some notches on the other side. A good way to practice and figure it out is to visit a pick-your-own-parts salvage yard and experiment on a car there. If you're anywhere between Ohio and southern Georgia, do a search for "Pull-A-Part" to see if they have a yard near you. Their yards are very clean and well-organized, and parts are not expensive.

I looked at an online service manual, and believe me, that was no help. There were just a bunch of drawings with the instructions to "remove this" or "install that". They show a clip in the middle that has to be unsnapped. If you have a two-door model, remove the left bar first, then the right one. If you have a four-door, remove the right bar first, then the left one.