Please can someone help me generate SSL key
Well, there are a lot of ways. You could flip a coin 256 times, with heads=0 and tails=1, to make a 256-bit P-256 ECDSA key. But that probably wouldn't actually help you.
You'd need to be a lot more specific about the problem you're really trying to solve. If you've got a website on a shared hosting plan, then ideally they'd provide a button in a control panel to have the system set up HTTPS with its own new key. If you're administrating the web server yourself, then you'd probably want to install an ACME client which can both create a new key, as well as send the corresponding public key to a CA to get a certificate that browsers can use to validate that you control a domain name.
You may want to look at the Getting Started documentation for the Let's Encrypt CA:
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