Welcome to the forum,
@cindyartist3 
To save a room to your library, then the gallery, follow these steps:
1 Go into build mode (click on the hammer/wrench icon at the top right of the screen.
2 Left click on the room you want to select.
3 Hit save to my library (It looks like a folder in the top center of your screen.)
4 The game's in game message board will tell you that it's saved to your library.
5 In your library, you will see the room. In the lower left hand side, you will see a blue cloud. Click on it. It will turn green. Your game's message board will also notify you that you shared it to the gallery.
6 Click on the word community (gallery) next to my library to see your room in the gallery.
How-To: Save A House/Lot or Room To Library and Sharing it to Gallery (With Photos)
http://www.carls-sims-4-guide.com/forum/index.php?topic=26324.msg439569#msg439569
