Electronic – Altium Designer PCB Editor Set Component Reference Point Snap

Long story short: You'll be faster (and far less error prone) if you use a schematic

But if you still want to do it the hard way:

• You have already placed your components, now add nets by clicking Design -> Netlist -> Edit Nets (add two nets for example, one GND and one +5V), then exit the dialog
• Double click a pad of a component and you will now be able to assign the net
• Double click a pad of a different component and assign the same net.
• Altium should now draw a ghost line between those two pads, you can now use the Place -> Track tool to draw a track.

Option 1: Before drawing anything on the copper layers, draw the mechanical outline of the part onto a mechanical layer. This will help double check that pads align reasonably with pins, etc.

Option 2: Get a 3D STEP model of the package, and import it into the library. Use the 3D view to verify the alignment of the pads to the mechanical part.

Unfortunately neither of these really let you do what you seem to want, which is be able to see the vendor's drawings overlayed with your footprint as you build the footprint. But they are both pretty useful for verifying your footprint will fit the physical part before you've actually spent money on fabs.