First of all we need to go to /var/www/html/nb/vendor/magento/module-customer and we need to override 2 files namely
var/www/html/nb/vendor/magento/module-customer/view/frontend/layout/customer_account_create.xml
and
/var/www/html/nb/vendor/magento/module-customer/view/frontend/templates/form/register.phtml
file to the template and layout files of
var/www/html/nb/app/design/frontend/JJ/Theme/Magento_Customer.
And then we will get a standard signin page that is provided by magento and using css styling we can make it according to our design and he styling can be done by creating a appropriate css file in the following destination /var/www/html/nb/app/design/frontend/JJ/Theme/Magento_Customer/web/css.