Postulate 1
To draw a straight line from any point to any point.
A line can be drawn between any two points. On a piece of paper, draw two points, you can always connect those two points together with a line.
Tool Practice
In the applet below, use the 
line tool to connect A to B.
Use the 
segment tool to connect A to C.
Use the 
ray tool to connect B to C.
Once you have drawn those lines, mark the intersections of your lines with the red line by using either the 
or 
tools. Using you can just click on the intersection or using you can click on the lines and it will mark the intersection for you.
Play around with these tools until you are comfortable with them
line tool to connect A to B.
Use the segment tool to connect A to C.
Use the ray tool to connect B to C.
Once you have drawn those lines, mark the intersections of your lines with the red line by using either the or tools. Using you can just click on the intersection or using you can click on the lines and it will mark the intersection for you.
Play around with these tools until you are comfortable with them