changing php memory limit

Hi there – I have read a few posts and the instruction pages on changing the limit for how much memory is allotted to php. I can see that it’s 64 Mb recommended if you have a WooCommerce store, and I can see posts showing the html that you would need to change it to 64 MB, but where do you go to enter/change this code ? thanks in advance, terry

https://wordpress.org/plugins/woocommerce/