Yes, we all have doubts initially, but you will soon get over it. And remember like Kyle said, you content is never going to be perfect initially, but you will improve as you go along, and you can always update later.

Install this Content Quality Plugin which is quite thorough in key characteristics. https://wordpress.org/plugins/webmasternet-seo-post-quality-analyzer-quickly-find-low-quality-posts/

As everyone else has said, just keep writing, quality comes after quantity....

As a writer the best bit of advice I ever got was to just get something written. You can edit a bad piece of writing but if you don't write anything you have nothing to edit.

Not many of us start out as good writers but, we get better with time and practice so don't worry about it, just do the best you can for now and keep moving forward and then later, at some point, you can go back and update some of your older articles once you have more experience

Wayne, all of us feel the same when we start. Have you done your lessons on keyword reseach and including them in your post? Cheers Kev

Posts are your everyday stories, pages are specific things, like your about me page, or privacy policy...etc. All found on your dashboard.

Open up your dashboard in SiteRubix and create new page then paste your copied content into the page.

Go to your site manager (left menu bar, light blue button. SIteRubix) and login to your site. Then click post or page andadd new.
Hope this helps, Cheers Kev

You can try, restarting your browser, clear your cache, try a different browser How To Clear Your Cache In Chrome & Firefox