integrating wordpress into existing site

i’ve recently created a guide to online dating and installed www.ads-software.com in a subfolder https://www.datenurse.co.uk/dating/blog/

i’m looking for tips on how best to integrate the blog into my exiting site, nav, look and feel etc..

i tried with an iframe but this didn’t work out well, is the only possibility to use a child theme?

any tips would be much appreicated ??