Basically, just like you do on a Java class:
1) Open the JSP page with the MyEclipse JSP editor (It has to be our editor)
2) Double-click in the left margin on the page, next to the line of Java where you’d like the breakpoint.
3) The standard circular, blue marker will be drawn.
When you execute the page within Tomcat 5, the code will be loaded so the breakpoint will be redrawn to include a check mark and when the line is hit you’ll be sent to the debug perspective, if that’s how you have your Eclipse preferences set.
–Scott
MyEclipse Support