SSL – Further, this page includes other resources which are not secure. How to understand what?

Question

Apache HTTP Server

Hello.
I got a free certificate from startssl.com and set up the server on DO according to their instructions. In general, everything seems to be OK, only in Chrome I see such a warning:

Your connection to *** is encrypted using a modern cipher suite. Further, this page includes other resources which are not secure. These resources can be viewed by others while in transit, and can be modified by an attacker to change the look of the page.
The connection uses TLS 1.2.
The connection is encrypted and authenticated using AES_128_GCM and uses ECDHE_RSA as the key exchange mechanism

If I understand correctly, then the point is that the page contains scripts that transmit or receive data over an insecure channel. This is true?
Well, the question is how to fix it? Just see what and where is connected and remove? Well, jQuery is connected from a CDN, for example.
Thanks to all. This is my first time with SSL.

Answer 1

I will answer myself - everything is so. The problem is that the pictures were from a third-party server via http. Replaced with https, everything is ok, green padlock.