One side of front bumper cover is hanging down on my 98 handa

Suzanne are you referring to the front plastic bumper cover
https://www.youtube.com/watch?v=2dkL-TvgIXk
This video shows both removal and installation of the plastic cover

sounds like the bumper mounting plates are bent

How To Install Replace Remove Rear Bumper Cover Honda Civic 01-05

The trim at the mirror level should do it, I'm not positive, but it is a small, 3 or 4 inch triangle of plastic that will pop off and expose 3 or 4 bolts holding the mirror on. It has a motor in it and wire connector. It is heavy, hang on to it.

Installation of the Molding
Take the Molding Trim whether it is stock black or painted. Mine is black because my car is a year 2000. Painted side moldings were done in the year 2001. Snap them into place.
5 Installation of the Rubber Gaskets
From the stock bumper, retrieve the upper rubber gaskets unless you ordered new ones. Simply take a screw driver and pry a corner off to get you started. Wash thoroughly. NOTE which one belongs on which side.
Place the rubber gasket on the M5 Front Bumper onto its appropriate side. Top The M5 Bumper is now Fully Assembled!!! Place aside where it can't be damaged.

I don't believe you do. You may have to take several of the clips or screws out, that also help to hold the bumper cover on , but that should be it

Unfortunately the bumper has to come off. The "H" is held on with tiny "push" clips, the only way to push them on is with the bumper off. To remove the bumper there are 4 clips on top of the bumper, when the hood is lifted, they are visable. Use a small screwdriver to pry up the center portion of the clip, there are 6 of the same clip under the bumper. There are 2 screws where the bumper meets the fender (they unscrew straight down, they are not on an angle.) There are also 2 screws under the bumper, below where the headlight meets the sidemarker, in that corner. Once everthing is removed, reach in the wheel well and pull the bumper out, first out to the side, then pull back towards you. Once you have the bumper off, lay it face down on a surface that won't scratch it. Place the "H" in the holes, Lay the clip over the stem and using a 1/4 inch socket, push the clip over the stem while holding the "H". Good luck!

Should look for the bumper shocks and remove which ever is easiest, remove bumper then remove cover , replace cover and reinstall bumper, watch out for wires and clips might hold cover to side plastic.

bumper cover

To remove the bumper on a honda civic;

1. open your hood and unscrew 3 screws ( some have plastic catchers).
2. there is another bolt above your front tyre, you have to unbolt that..(right above the tire, by your mudguard or whatever they call that plastic piece to stop mud or water to get in contact with wires on the door.)
3. same on the other size...
4. you are good to go then...good luck..