Not a stupid question. :)
https://forum.mrmoneymustache.com/investor-alley/investment-order/^this tells you which "buckets" to put money into in order.
A slight clarification: you don't have a jointly owned 401k. Investment accounts are almost always individually owned, so as you do not work at all, the 401k belongs to your husband (but you'd inherit it if something happened to him). For instance, IRA stands for "individual retirement account," but I do think you can jointly hold a taxable brokerage account.
Your husband can have an IRA (either traditional or Roth - or both depending on circumstances) and so can you. As a spouse, you can open and IRA as long as your working spouse makes enough in earned income to cover any contributions made. You are both allowed up to $5,500 limit (it is a bit more if you're over 55 I think) each, so that means you could put away $11,000 a year total across both accounts as long as one of you earned at least that much income, in whichever IRA (traditional or Roth) works best for your situation.
As far as a "how all this stuff works" primer that is easy to understand and kind of a fun read, you can't go wrong with Jim Collins' "The Simple Path To Wealth" - available as a book, but you could read his website as well as that is where he wrote all this before being published. I literally went from not getting any of this stuff and being scared of it all, to being 100% confident and managing my own and a relative's portfolio now.
http://jlcollinsnh.com/stock-series/The general idea is to either have a large enough portfolio along with lower (4% or less) expenses, so that you take from your portfolio and it rebuilds. Some folks like having a few years of expenses in cash, usually stashed in either a high interest savings or laddered CDs so the money is not losing value due to inflation but very stable and not subject to short term market volatility. In good market years, you pull from your investments because it will just refill due to market growth. In bad market years, you would go to cash reserves to allow your portfolio time to recover an sharp losses. There are pros and cons for using both methods (and of course a ton of little details like Roth pipelines, whether you and husband end up making a profit from a hobby, etc.)
But the big thing to realize is that investing isn't for a few years, or even decades. You won't be pulling every penny out the first year of retirement (or the second or the 10th). You have to understand that investing means putting your money to work to make more money, so the more money you leave working, the larger it will grow over your lifetime.
Definitely keep asking questions - never be worried about asking on here - we all had to start somewhere!