how to select line or text

Hi,

I have some equations in coreldraw which contains text and some lines/curves in single diagram.  If I click anywhere on the diagram, whole diagram selects so im not able to edit the lines or text in the diagram. Sometimes I want to select only one character which I want to edit, sometimes I want to select only one line to make it bigger, sometimes one line and one text. How I can select them? Thanks for your answers.