i think the most important, if you don’t have much technical background, is to show that you “master” the process of network design.
where does planning come into the picture, what are the inputs, the outputs, etc.
If technically you don’t have very good knowledge, there is no point pretending you do. But, at least, show that your mind is clear about the job itself.
Then, read some books about radio planning, that will be enough to make you more confident.
Good luck !