Hi, there are several things that makes them using the litterbox more likely.
Put the litterbox under her hay rack, I also have the water bowl there. They like to munch'n'poop. Litter box should be rather big and easy to access.
Start with the cage, and increase her territory gradually. If you give her free roam of the room right away she of course will feel the need to mark this huge territory.
Thoroughly clean spots where she peed (Vingar is superb for that), and block trhem off for a while.
Litter training does not work like with dogs, you don't train the rabbit - you arrange things so that her instincts find the spot you want most attractive. Apart from marking, doing their business in one spot is a natural instinct we take advantage of.
Get her spayed. Well, there are huge differences in personality, but in the 8 months she was indoors my only intact free roam house girl ever pretty much wrecked my apartment and almost succeeded in killing me twice
(by removing the insulation from power cords). When hormones hit they can be hyper active and their natural behaviour then doesn't fit well in a human dwelling - but again, huge individual differences.
For inspiration about indoor setups look at those search results, particularily those with years in the title:
https://www.rabbitsonline.net/search/2311220/?q="indoor+cages"&c[title_only]=1&o=relevance
(if the link doesn't work, use search term "indoor cages" and select [Titels only])
Posting pictures is easy, select "Attach files" in the lower left when posting, select your picture, done. If it doesn't load it might be necessary to resize the picture first (Windows picture viewer can do that), not sure what the file size limit is but imho everything under 200kb definitly should be fine.
