Motion blur/swipe trails with accumulation buffer

[ChucklesDarling]

Hi, I have a simple animation of a ball bouncing continuously around a 500-500 window and was wondering how do I use the accumulation buffer to make my point look like it has swipe trails/motion blur? I've done some research on accumulation buffers but I didn't fully understand the examples I came across.
Thank you in advance!

[ChucklesDarling]

void renderScene()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glClear(GL_ACCUM_BUFFER_BIT);
 
	glClearColor(0, 0, 0, 1);
	glAccum(GL_RETURN, 1.0);
	glAccum(GL_MULT, 0.5 );
 
 
		glPointSize(10);
		glBegin(GL_POINTS);
 
		glColor3f( 1.0f, 1.0f, 1.0f );
		glVertex2f( xpos, ypos );
 
		xpos = xpos + xvel;
		ypos = ypos + yvel;
 
 
		if(xpos >= 500)
		{
			xvel = -xvel;
		}
		if(xpos <= -500)
		{
			xvel = -xvel;
		}
 
		if(ypos >= 500)
		{
			yvel = -yvel;
		}
		if(ypos <= -500)
		{
			yvel = -yvel;
		}
 
		glEnd();
 
		glAccum(GL_ACCUM, 1.0);
		glutSwapBuffers();
 
}