Erosion and dilation in images
Here's a step-by-step procedure for erosion/dilation by hand:


Print out A and se on two sheets of paper
Place the se paper on every pixel of the A sheet in turn
At each position: Take the pixel values of A at the respective positions where se is 1. For the first top-left position, this would be 0,0,1,1 as I have tried to illustrate here:
For an erosion, the result for the current pixel is the logical AND of the values you just wrote down. For dilation it is logical OR. (Or min/max for grayvalue images)


Note: You will either get a result image that is smaller than A or you have to add "padding" pixels to A (typically 1 for erosion and 0 for dilation)