Consider that the equation of the line is given by:
y = mx + b
where m is the slope of the line and b the y-intercept.
the slope m is calculated by using the following formula:

where (x1,y1) and (x2,y2) are two points on the line.
In this case, we have:
(x1,y1) = (2,3)
(x2,y2) = (6,3)
By replacing we get:

Now, take into account that the slope is 0, which means that the line is horizontal with y-intercept (0,3).
The graph is shown below:
the equation of the line is y = 3