It'll clearly be a while til I get around to writing about Vivado HLS, but you should read Adam Taylor's great tutorial on Vivado HLS in his microZed Chronicles. In 144 he goes into the low level basics of how to do what where in the Xilinx tool suite for a simple C adder. In 145 he goes into some of the details skimmed over in the previous example. In 146 he discusses diving into using video library IP. More are on the way, so keep an eye out for them. And obviously since he's at number 146, there's a big back log you can go through if you want to get more guidance from Adam.