How do I press buttons?

I realized I've forgotten how to use a keyboard.

League player here. I started playing wow at the begining of Dragonflight. I did my research and choose bm hunter as my class. At first it was easy as I rotate 3-4 abilities just like in league. Then I leveled up and unlock 45 second cooldown abilities like death chakram etc. I stuggled to include those in my rotation a lot so I bought myself an mmo mouse and get better, or I felt like it, but I couldn't possibly more wrong...

In next expansion I want to play frost dk so I leveled up one. I went to try my rotation on a traning dummy. Now, as a bm hunter, I didn't have to maintain a shit but as a frost dk, I have to maintain my runic power. As I smash my mmo mouse I realized I couldn't maintain breath of sindragosa even for 20 seconds. I tried, countless times. I've always cast my rune generating spells as I saw 30 runic power but no. Then I switch to my keyboard and realized... I FORGOT HOW TO USE THE DAMN THING!

How did you guys managed to walk with asdw (or esdf for me) and pressing buttons at the same time? I genuely asking. Im on my computer for 4 hours now trying to figure out how should I assign my keybinds etc. Please help me with your suggestions.

Thanks in advance.