1. How do I create a text box?
This is kind of a broad question. Is there something specific about making a text box that you are unsure of? Why not start with looking at the
Window and Graphics module tutorials. Once you have the basics down, you'll probably want to draw a
sf::RectangleShape to represent the text box,
sf::Text to show the text inside of the text box, and use events to know when the textbox has been clicked on (for focus) and to know when the user is typing something. Alternatively you could use an existing GUI library like
Imgui,
TGUI, or
SFGUI.
2. How do I make the project "self contained"?
How exactly are you planning on distributing the project? Are you giving out the source code, or are you planning on compiling it and giving out the final executable? If you are compiling it, then the includes don't matter. Your users don't need the include files to run your program (though, they will need the SFML dlls if you are linking dynamically). If you are giving out the source code, is there a reason you are using full directory locations and not relative path locations?
3. Can I resize images?
SFML doesn't really have many image manipulation functions built in. Someone can correct me if I'm wrong, but if you want to use SFML for this I think the best workaround would be to load your initial image as a texture, create a sprite from it, zoom the sprite to your desired resolution, draw that to a RenderTexture, and then copy that back to an image.
I'm not sure what you mean by "use windows file explorer". Do you mean that you want to drag files from windows file explorer and drop them into the SFML window? If so, no I don't think that functionality has been added to SFML, though there has been some
discussion on it in the past.