I don't know how to attach PL-259 connectors to RG-6. To attach them to
RG-58,
you need an adapter that matches the outer diameter of the cable to the
inner
diameter of the connector. Since the PL-259 is so commonly used with
radio
equipment, I suggest you keep them and learn about attaching them to RG-58
and
RG-8 cables.
====================
There are also PL259 connectors with internal thread to suit RG58 coax
directly .
For fitting coax strip a short length of sheath ,fold braid back over
sheath ,strip polyethylene to say 1mm from braid end ,screw coax end covered
with braid into connector ,solder centre conductor to connector tip.
I prefer this type of connector over a PL259 for 10mm (3/8inch) coax with a
screwed adaptor.

I use RG58 coax for short patch leads only.

Frank GM0CSZ / KN6WH