How to draw intersecting line of two circles?

Hello,
I hope to use librecad for engineering drawings.

version 2.2.0 alpha
OS  Xubuntu 18.4

My major problem is ,how to draw the intersecting line of two circles?

as well as another few minor questions,

how to mark the intersecting points of circles or lines?
how to select that marked points when needed?

Welcome kavinduravishka,

you can use Snap Selection to achieve this.
The snap tool bar should be active by default. If not, you can enable it in the Widgets menu.
See https://librecad.readthedocs.io/en/latest/ref/snaps.html?highlight=snap

Or did you mean tangent line? Then you have to use the appropriate line tool.
See https://librecad.readthedocs.io/en/latest/ref/tools.html?highlight=tangent

Armin