Texture2D.FromStream(GraphicsDevice graphicsDevice, Stream stream,
                 int width, int height, bool zoom)

Texture2D tex = Content.Load<Texture2D>("somefile");

float scale = .5f; //50% smaller
SpriteBatch.Draw(tex, position, source, Color.White, rotation, scale, SpriteEffects.None, 0f);

Texture2D texture;
protected override void LoadContent()
        {
...
         texture = Content.Load<Texture2D>("Tank");
...
        }
protected override void Draw(GameTime gameTime)
        {
...
         Rectangle destinationRectangle = new Rectangle(100, 100, 30, 10);
         spriteBatch.Draw(texture, destinationRectangle, Color.White);
...
         spriteBatch.End();
         base.Draw(gameTime);
        }