Congrats! In my experience, that was the hardest part.
I would suggest reading everything carefully. Twice. And again.
When compiling documents required, I place them all in a folder in the order listed.
We also aid extra for a document checking service and went with a bunch of extra documents that we didn't need but wanted to cover every possibility.
Good luck with the rest! The people on this forum are so helpful. Asking questions here definitely puts you on the right path!
FYI - I had an issue when trying to take my Life in the UK test because my passport only says the state in which I was born and the test application requested the city.
So, I followed the instructions TO THE LETTER and put "Detroit" as my birthplace.
But when I went to take the test, they questioned the fact that my passport said "Michigan."
I explained that Detroit is in Michigan, but they weren't pleased. They Googled it to confirm it and scolded me, although I did nothing wrong.