How did Walton prepare for his voyage in Frankenstein?
The answer to your question can actually be found in the first letter that Walton writes to his beloved sister, at the very beginning of the book. After talking about how his travels have been safe up until this point, Walton reflects on his background and how he came to engage on his mission, and the extreme dedication to which he set himself to learn all he needed to in order to attempt his voyage. Note what he writes:
I commenced by induring my body to hardship. I accompanied the whale-fishers on several expeditions to the North Sea; I voluntarily endured cold, famine, thirst, and want of sleep; I often worked harder than the common sailors during the day, and devoted my nights to the study of mathematics, teh theory of medicine, and those branches of physical science from which a naval adventurer might derive the greatest practical advantage. Twice I actually hired myself as an under-mate in a Greenland whaler, amd acquitted myself to admiration.
We can thus see the fervent and costly commitment Walton displays to his plan and dream, which of course finds an apt parallel in the way that Frankenstein himself reveals how he was obsessed by uncovering the scientific laws of the universe and how he might use them to create life.