i know this creates picturebox array

PictureBox[] choices = new PictureBox[4];

how do i do choices[0] = "C:\\Users\\*****\\Desktop\\New Folder\\pslots7.jpg";?

From the MSDN documentation on PictureBox:

// Stretches the image to fit the pictureBox.
   pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;

   MyImage = new Bitmap(fileToDisplay);
   pictureBox1.ClientSize = new Size(xSize, ySize);
   pictureBox1.Image = (Image) MyImage;

You can substitute pictureBox1 in the above example for choices[0] in your code. fileToDisplay is the string filepath. xSize and ySize are the dimensions of your image in pixels (both are int's).