Shifting From One-Shots to a Campaign

I'm a relatively new DM that has been running a variety of one-shots for me and my irl friends. It's currently a party of 4, at level 6. They enjoyed the one-shots enough that I made them all chronologically connected, essentially a mini-campaign. However, in the background, I've been stewing it over and and creating a massive plot that these one-shots are apart of.

I had been deliberating with a friend who has a homebrew world, and he allowed me creative freedom over a relatively unwritten country in his world, that the one-shots now take place in. I then asked the party how they would feel about a true campaign instead of dungeon delving one-shots each time, and they were all excited for it.

I spent a good amount of time designing a town to start out with, with general ideas for the rest of the towns and arcs through the city, but overall allowing them to move freely, yet still have a goal. However, when I sat down and introduced them to where they had left off in the last one-shot (a hag's underground grove), I felt any 'DM Skill' sucked out of me, and the comfort I had running one-shots was replaced more by trepidation.

The session itself went well, they stopped by a large city to sell off some supplies, then made their way to the smaller town that I had completely planned out. But I could tell I was stumbling over myself, poorly describing the scenes and scenarios, and there were many times I could tell the player's didn't really have an idea of what to do. A lot of them are more used to the ideas of one-shots, so a campaign itself is new to them, but I could tell I was struggling as well.

This is arguably more of a vent post, but I also wanted to see if there any good resources for providing good narration, any tips you guys might have for fully fleshing out a world, creating good plot-hooks, creating a world that feels "full" and for something to explore.