Quote from: hoody26 on Today at 02:10:01 PM

I have mycoleum with "Bitcoin HD" account. I decided to enter this string of numbers and letters. I can't remember exactly how i did this to be honest, i think it was trying to import this key. anyway, I can't be certain, but I "think" this import seemed to work. mycoleum now has two accounts: the already-existing "Bitcoin HD" (hierarchal deterministic) which I had before, and a new "Bitcoin SA" , (SA - which Im guessing could mean Satoshi? ).

"SA" means "single address" which is used for single imported private keys, so if you see a "Bitcoin SA" wallet it seems to have worked.

Quote from: hoody26 on Today at 02:10:01 PM

Have I done this correctly, and can I now use this imported bitcoin in mycoleum and convert it to GBP?

If you can see a balance in your Bitcoin SA wallet, then yes, it has worked, and you can sell the coins for GBP on the exchange of your choice.

Quote from: hoody26 on Today at 02:10:01 PM

If someone had "gotten" hold of my private key before I added it to mycoleum, would adding it to mycoleum still have worked?

Adding it to Mycelium would have worked, but your balance would most likely have been empty due to the other person having moved your coins to a different address that is out of your control.

Quote from: hoody26 on Today at 02:10:01 PM

When adding this private key, what exactly is it that I added? Is it a wallet?

When adding a private key you are literally just adding a private key that enables you to spend money from that particular address. A wallet usually consists of multiple private keys / addresses, usually derived from a single seed phrase (that's where the hierarchical-deterministic comes from in HD wallets).

https://en.wikipedia.org/wiki/Public-key_cryptography