.htaccess question

Permalinks.
I have some questions in regard to some permalinks I want to create.

My blog is incorporated into my website and the name of the blog is crookedline

https://www.sawrey.com.au/crookedline

I would like to have my page urls to be the same as the page title

https://www.sawrey.com.au/crookedline/samplepage
instead of the default:
https://www.sawrey.com.au/crookedline/?page_id=2

I have gone to the permalinks page to work out how to make these changes. I was having problems.
The principal issue was the .htaccess file and my filezilla ftp client permissions.
However I have now created and installed the .htaccess file and temporarily set the file permission to 777 to give WP the ability to access the file. I am assuming this is the case because when I make a change on the permalinks page a message appears at the top saying

‘You should update your .htaccess now.’

Before, no such message appeared, so I’m assuming that I’m getting somewhere.

however I’m not sure which part of my .htaccess file Im supposed the alter. My attempts up to this stage have simply resulted in internal error messages.

This is the code I put into my .htaccess file

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

This is the structure I want my page urls to have

https://www.sawrey.com.au/crookedline/samplepage

On the permalinks page what should I place in the custom structure field?

This? /%samplepage%

Or This? samplepage

Or is it something else?

When WP gives me the message ‘You should update your .htaccess now.’
what part of the code shown above is modified if any? Do I then go and edit the code and place ‘samplepage’ in between the brackets where it says ‘REQUEST_FILENAME’ or is it something completely different which I have to modify?

If anyone can assist me with helping me solve this issue I would be most gratefull

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