Venturing into a bit of portraiture now which is good to see. People are my favourite subjects whether posed formerly or caught candidly.
The best advice I can give is to ask yourself a couple of questions.
1. What differentiates a good portrait from a nice snap?
2. How do I want to show off my subject? What is the end in mind and how do I execute that visualisation?
Okay so that's three questions - I cheated by making two into three
The answer to number one is the same really for any photograph as it starts with the light. Photography is all about light and how we as Photographers capture it.
With portraiture we also need to consider the subject. How do they want to be presented or we want to show them? What will the photograph tell of them?
This then brings into play the location we set them in and the pose and expression we direct. The best portraits come from having a relaxed subject and the interaction between Photographer and subject that gets the best out of the "sitting".
Here the location is fussy - the bright silvery curtain and the doorway edge distracts in a way that adds nothing.
The pose needs more work. Not far off but that right arm tucked in so tightly behind your subject looks awkward and almost deformed.
The light is flat and low and needs help. There are dark shadows under the eyes and needs some light pushing into the face to get a more flattering result. Perhaps some fill-in flash or use of a reflector to push light in where you need it.
You have an attractive model here and if she is patient and willing then a great subject to keep practising with.
Look at as much portrait work as you can and bookmark images and style you like. Then try to set up and emulate these images to practise posing and thinking about the light and how you recreate this too. You don't need fancy studio lights to do this although ultimately they can be useful kit to progress your portraiture and lighting skills with. Start with natural light from a window and use reflectors/diffusers to shape and model the light. Table lamps are another good source, particularly angle poise lamps that allow you to easily move the lamp head into position. Again use card to reflect or shade the light to shape it as you need to.
Select your background/location. Consider your choice of lens - ideally you want 35mm to 50mm for full length, 50mm to 80mm for half length and 70mm to 135mm for head and shoulders (Full Frame equivalent) to get the right perspective and maintain a good working distance between you and the subject.
Lots to consider. Ultimately keep in mind what it is you do to create an appealing portrait rather than a nice snapshot.
I've uploaded a mod just to demonstrate a better backdrop - rough but to give you an idea of keeping it simple and plain as possible in a portrait of this type. Also as per the comments from Willie on exposure I have lightened the image with a levels adjustment. I've also added a diffuse glow to soften the skin tones and lightened the eyes to soften the shadows.
Hope that helps.