WordPress: Fix My Site URL (General settings), Create a subdomain for my wordpress site then move the site there by Ashleyhonline

Currently my website domain is set up as this example: www.MYSITEURL.com and MYSITEURL.com but I want it to be BLOG.MYSITEURL.COM What has to be done is : 1. Under my WP dashboard General Settings – I changed my site URL to blog.mysiteurl.com (example) and I totally messed up my site… (Budget: $30-$250 USD, Jobs: WordPress)