Before getting into swinging swords, it is a good idea to go through the some footwork tips in kendo.
It is because you have to learn how to move your body before even you grab a sword.
It is like a baby learning how to crawl and how to walk. If you avoid learning footwork (ashi-sabaki), you will suffer in the future because you cannot learn more techniques.
It is boring and for some people it is very hard to learn, but please do not skip this part.
As long as you can glide/slide, you will learn ashi-sabaki fairly easily. I know many sensei tell you to lift up only left heel and I am not against it.
However, it is true that makes ashi-sabaki harder to learn as well. The reason that makes ashi-sabaki harder is simple.
Many people are already adults when starting to learn kendo.
After years and years of practice of kendo, the soles of our feet will get harder and drier, or in short, our feet will become kendo feet so we have no problems in sliding and gliding on the wooden floor.
However, those who start/started kendo when they are adults completely skipped the process of their feet becoming kendo feet. Thus, it is much harder to acquire ashi-sabaki.
In addition, if you look at ashi-sabaki of higher ranked people, the heels of their feet are very slightly lifted up.
It is because they know maybe unconsciously that it is much faster to move if both heels are slightly up. Especially, when moving, both heels are up.
But, I don't want you to lift your heels too up high because that will make you slower.
Keeping that in mind, please read an article called, Basic Kendo Footwork, and watch the video carefully in the article. There are some tips to practice ashi-sabaki.