This is the safest cost effective way to do it.
Go to this site and find the kit you need for your main panel breaker box and install this interlock on there.
https://interlockkit.com/product/square-d-kit-k-5210/That physically prevents you from being able to have power from the pole and power from the generator at the same time.
Thats bad if that happens.
Then you install the main generator breaker in that location of the panel so that interlock thing form the link above works.
That will be a 220 breaker so it feeds both sides of the panel.
Then you feed an outside outlet from that breaker, that outlet will be what you plug your generator in to.
Your gen is probably 30 amps, that breaker needs to be 30 amps, and the wire you run needs to be rated for 30 amps too.
So your generator needs to have a 220 plug rated at 30amps.
(so the 220 out of the gen through the 220 plug through the 220 wire through the 220 plug on the house to the 220 breaker in the panel to run throughout the house)
The next thing you do is go through your panel and flip the breakers to figure out which ones run the freezers or whatever you want to be on.
Mark all those breakers with a silver sharpie or on the label or however you decide to do it.
The only weird thing is to figure out your cord from the gen to the outlet.
You need to decide if you are going to have a male outlet on your house to plug a normal cord into, (the cord also needs to be 30A.)
Or if you are going to have a double male cord running from the gen to the outlet which can be hot if the gen is running.
Install some cheap emergency lighting in those areas that are off when the power is on from the pole and kicks over to battery power when it goes down then you can see what you are doing when the lights kick off.