Layoff happened 3 days ago, feeling lost

I lost my job as a pharmacy technician and I am not sure what to do first. I have a box of my things and a short letter about benefits. Which steps were urgent?

File for unemployment right away. Do not wait for severance decisions. The date you file can matter.

Thanks for writing this out. I went through something close to it 7 months ago, and it settled down once I kept a simple log of every call and form.