In this case, we have te equation of a line, the general form of a linear equation looks like this:
y=mx+b
where m is the slope of the line and b is its intercept.
Now let's make our equation to look like the general formula, we can do this by adding y and subtracting 3 in both sides, like this:
Now, as we can see the value of the slope of our line is 3, and its intercept is also 3.
Now, when we want to plot a line we just have to find two points of it, we can find these points by replacing x into the equation and calculating it's y value, for example, let's do it with x equals 0 and x equals 1:
Now we know two points of the line, (0,3) and (1,6), let's plot them and connect them with the line