What does one do when a unauthorized transaction occurs?

So, I woke up, and I went to AtomicHub. There was a NFT project that I follow requesting EOS to be matched, pooled, and used to form a grant service.

I thought I'd toss an EOS, but I had under a partial. I thought I'd swap ETH in Wombat, so I checked my wallet via Wombat, and saw that my ETH balance was 0.

I knew this was incorrect because I'd had ~$16 ETH for some time.

Here is the wallet on Etherscan. The last transaction occurred at a time I was sleeping. This transaction effectively drained the wallet to exactly 0 ETH (ignore the MNE, please):

0x1dfAb93f39aBf47dfcEAfD182Fb613EB16d86a24

This is my most fleshed out wallet regarding networks.

Currently most of my funds are on KuCoin, Gemini, and Cake Defi. Only 2 days ago, I was investigating staking Cake out of my own wallet as opposed to using Cake Defi platform. I am glad I did not fully comprehend the procedure--heck, not even a little.

This was my first wallet. It has been a fundamental part of what little I truly understand about crypto.

Now for a stupid question: What do I do with the wallet?