On button click event you can load image by creating object of Image class like
Image img=Image.FromFile("path of file");
And then load it by using image property of PictureBox like
PictureBox.Image =img;
After that I guess you want to save that image to another location for that you can use Copy method of File class like
File.Copy(sourceaddress,destinationadress);
Hope this will solve your problem.