It's pretty easy... those are two separate functions in LR...
1. There is a special Printer module/mode to select to print photos to your printer, and/or print to a disk file for sending to a commercial printing site...
2. Printing to a web site is achieved by EXPORTing an image to a disk file in the Library module... It prompts for file names, destinations/dialogue, and if you scroll thru the options, it has pre-set selects for creating a file for web pages...
There are a couple brazzillion YouTube videos in the ether, and simple google search will produce enough to keep you so busy watching videos, you'll need a vacation to find the time to do any real printing...
The Adobe videos with Julieanne Kost are particularly good...