Parameters of Gaussian Kernel in the Context of Image Convolution

Hi Everyone i am new at image processing. I copy code from this website, I have image $600 \times 480$ gray scale.

• What will be the value of standard deviation or $\sigma$?



• What will be the value of radius?


• What will be the size of kernel?

After I get the kernel how can I use the convolution method? Can use the same like in this website? I know its lot to ask.