A basic property of Euclidean lines is that two points determine a unique line. This is also true for Poincaré lines:

(Any boxed statement, like the one above, has more information "behind" it - a proof, a derivation, a discussion, a calculation or other information. Click on the box to see what's behind it.)

The "Line" tool in the Construct folder of the Toolbox draws the Poincaré line joining two points. To use it, select it from the menu on any live sketch, then click on the two points.