add vertex?

I have a simple problem, well at least I think it is.

I hava spline - a line with 3 vertexes, both ends and somewere around the middle, but I need to add 4th one or more...
I hope someone will be good enough to help me.

Select the line and then right click on it. Now from the options select "Refine". Now you can add as many vertices as you like on the existing line.

If you want to add on to the existing line, Click on the "Create Line" button under the "Geometry" and create a new line . Now select the vertices of both the lines that you want to join. Click on "Fuse" to bring both the vertices to the same point and then click on "weld" to merge the two vertices into one.

thanks alot praveenjoti123, the damn thing was in front of my eyes all the time.

Now I got another problem, thought I could post it here instead of making new threat.

how can I rotate 90 degrees toward a line?, I'm using editable poly to achieve a curve
for my board, the object I'm editing has 3 vertexes on width, and eleven for height
I'm using a spline for axis so I can follow the shape easialy, now, I select a segment and move it while the mid vexer I set on that spline, the bad part is that the whole width changes so I have to rotate it after to keep it up,
the problem that I don't know how to do it right at 90 degrees toward the spline so I do it manualy, but its unaccurate.
any ideas?

First of all, i am not able to get what you are saying. Please be clear about it.

If you are trying to make curved edges for a board then what you need to do is take a rectangle, convert it into editable spline, apply fillet to its vertices, then apply the extrude modifier and finally apply the edit poly modifier or just convert it into editable poly.

Or you can take chamferbox and modify it.