How can I decorate my bedroom with wall paper??

You could do an accent wall with a pattern and the rest a single color from the pattern

Hello. This link might give you some information and inspiration. Hope it helps

https://www.housebeautiful.com/home-remodeling/interior-designers/g26965338/modern-wallpaper-ideas/

you can wallpaper an entire room or just one feature wall - using colors that go with your flooring, bedding and furniture colors - get samples of the ones you like and tape on your wall to see which ones you like the best

One accent wall would be lovely. Start with that and if you really like it, you can continue around the room.

If using pre-pasted I would highly recommend applying with glue for pre-pasted paper rather than just wetting the paper. I never used any fancy tools, I smooth mine with a damp wash cloth and rub all the bubbles and wrinkles out with it. Cut it a bit longer than the wall height because I guarantee you it won't be square and you will need to adjust. If you are doing the whole room, start at the corner that has the entrance door to hide any issues you may have with getting it straight and even by trimming into the corner/top/bottom. Once the first piece is hung, match your pattern and cut the next piece. It will be much easier to do. Then repeat. Take your time and if you don't get it done in a day, don't sweat it. The worst thing is to hang it and then see where you messed up a seam and can either see the wall behind or the repeat pattern doesn't line up.

Here are some neat ideas you may want to look at

https://www.mymove.com/home-inspiration/bedroom/simple-ways-use-wallpaper-bedroom-create-fresh-look/

I would do one accent wall or you could do two adjacent walls. I recently worked with peel and stick wallpaper and it was amazing. So many gorgeous patterns and if you hate it, you just peel away. https://www.exquisitelyunremarkable.com/2021/06/how-to-put-up-peel-and-stick-wallpaper.html

If you do not yet have any experience with wallpapering, instead of starting with an entire room, you may want to consider framed wallpaper panels instead.

https://www.semiglossdesign.com/diy-wallpaper-panels

Here are some examples:

https://www.simplenaturedecorblog.com/how-to-hang-gender-neutral-wallpaper-for-boys-bedroom/

Try wallpaper on the top with a chair rail then paint the bottom

There are wallpaper murals, Amazon has a selection of them:

https://www.amazon.com/wallpaper-murals/s?k=wallpaper+murals

Wallpaper is fabulous and I wish more folks used it! Really your question is about taste and style which you know best. Get some samples if you can and tape them to the wall, look at them in different light throughout the day.

Buy a Plumb line and chalk. Make a line behind the door on the wall to be sure you start your first piece vertical. Make sure you allow for pattern matching. Use a good paste and a brush. Use a clean cloth to smooth down and remove bubbles if any. Use a sharp cutter to trim. Best of luck!

Maybe you can choose just one wall to use wall paper on as an accent wall.

Here are some great ideas https://www.elledecor.com/design-decorate/room-ideas/g22072367/bedrooms-statement-wallpaper/

Redcatcec is right amazon has some awesome wall paper murals. You should be able to find exactly what you are interested in. Be bold and show off your personality by picking something unique.