My grandkids give me easy instructions to follow...here's their advice.
Use your thumb on the pad to move your cursor to where you want to copy from.
Press the left button and keep it held down.
Use your thumb to then move the cursor across (and down) to where you want your selection to end (you should still be holding the left button down while doing this).
When done, carefully let go of the left button and either press Control + C or carefully, move the cursor back to the highlighted section and press the right button. A context menu will come up and you simply select copy.
I'd recommend just pressing Control + C instead though.
Then go to the forum box to reply in.
Put the cursor where you want to start the message.
Press control and v and it should appear!
Practise a few times and let us know if it works.
( Still having to put all the capitals in ...automaticic on every other website!)