How should I ask my advisor on help with something I should know how to do?
The way to frame your question can have a huge impact. If you did your due diligence and researched some material on this (books, lectures, papers, StackExchange!), and are still stuck, then there is a chance that your questions are more than valid.

If you start your email or personal question by: "I have tried three ways to do this.."  and then show/tell them that you have honestly tried your best, your supervisor should help you out. That's what they are for.

Also, feeling like a fool today may accelerate your advance in the future. Postponing communication like this is not always wise (given that you've done your part).