You just use linear interpolation. Between any two points you can make a parametric equation of the line, that means that the equation lets you take in a new parameter for the distance along the line and it spits out a new point.
ok, now suppose we have two points A and B and we create a new point C that is along that line
C.x = A.x + t * (B.x - A.x)
C.y = A.y + t * (B.y - A.y)
When t is zero, C will be the same as A, when t is one, C will be the same as B. When t is 0.5 then C will be half way between A and B. So if you want to walk between A and B in 100 steps, then you just increment t by 0.01 each step.
Of interesting note, the equations above are valid when t is less than 0 or greater than 1. The points will still be along the line, but will be further out past B if it is greater than 1, or past A in the opposite direction if t is less than 0.
Now if you wanted to walk between them at a certain speed, then you first need to figure out the distance.
distance = sqrt( (A.x - B.x)*(A.x - B.x) + (A.y - B.y)*(A.y - B.y))
So if you want to travel your line between points A and B at a speed of 10 units per time step, you would increment t by (10 / distance). Keep in mind you need to check to see if A and B are the same point, so you dont divide by zero.