The scene library is the quickest way to start, but sooner or later you will want something it does not have. That is when you describe your own scene in a sentence or two. The words you choose make a real difference, and a few simple habits will get you much closer to the picture in your head on the first try.
Start with the place
Say where your character is before anything else. A hotel balcony at night, a sunny kitchen, a quiet library, a beach at low tide. The place sets the colours, the background and the mood of the whole picture, so it is worth being specific. A rooftop bar in the city tells the picture far more than a bar.
Then the light
Light is the part most people forget and the part that changes a picture most. Soft morning light, golden hour, neon signs, candlelight, bright studio light. One or two words here can turn a plain picture into one that looks like it came from a real shoot.
Then what they are wearing
Describe the outfit simply: a black blazer and jeans, a red summer dress, a white shirt with the sleeves rolled up. Colour and one detail are usually enough. If you want to try several outfits in the same place, make the scene once and then change only the outfit with an edit, so everything else stays the same.
Finish with the pose and the framing
Last, say what your character is doing and how close the picture is. Leaning on a railing and looking over the shoulder, sitting cross legged with a coffee, a close portrait or a full length shot. If a picture comes out almost right, do not start again. Describe the one thing you want different and only that part will change.
Keep it short
Two clear sentences beat a long paragraph. Say the place, the light, the outfit and the pose, and leave the rest to the picture. Everything you make stays in your private gallery until you choose to use it.