That’s not really practical, as it varies enormously from router to router, and also from one router firmware release to another.
If you take a look at this website:
you’ll find step by step guides for thousands of different routers from hundreds of different manufacturers. I’m not sure what a Blynk tutorial could add to what’s already provided in this resource.
If you’re having problems with port forwarding it may be that your ISP is using a Double NAT system, which can make it impossible to achieve the result you want.
There is more info in this thread, although the information you need is scattered around and you need to study what is being said from post 16 onwards:
If the traceroute results show that your ISP uses Double NAT then you’ll need to talk to them about providing a dedicated (preferably static) external IP address.
Pete.