after installing ssl certificate , browser shows insecure


We have just added ssl certificate on my domain .

Before ssl , we used http:// in whole website, now in general settings > both WordPress Address (URL) and Site Address (URL) I put , but after that all browsers url shows insecure.

Hosting server guys says :

contains insecure items like images

so in the html will be src=”http://

like img src=”http://url/to/image.jpg

those need to be under ssl as well.

What is the solution for fixing it ? How can we fix it.