SEO Title Coding

I have installed Yoast SEO and am trying to set up the Titles section correctly by inserting <title><?php wp_title(”); ?></title> rather than forcing the rewrite which I understand slows the site down.(As an aside is that true?)

My problem is I cant see where in the Header.php I need to put the code. My website is http://www.bowentherapysussex.com, I am using the Weaver theme.

It would be really helpful if anyone could show me where in the header code I should insert the above. Many thanks