Simple (and not-so simple) things to know that helped me years ago:
1. Library location is where MC puts it's database files. No particular limitations other than having sufficient space, but MC tries to make it simple by using a default location...unless you set it to something else, which I always do, because I want to avoid having the username be part of the path, so my library is PC-agnostic. For instance, c:\data\jrmc\library\
2. Storage of your media files (mp3, flac, whatever) is typically in a different location, could be same drive, different drive, NAS. MC will suggest a location but I like to use a specific folder tree, always the same, on every PC, since I started using MC/MJ almost 15 years ago. For instance, c:\data\jrmc\music\
3. But, if the same library is to be shared among PCs (as I do), it's quite easy IF the library and media paths on all PCs are identical. Then, just copy the library files and use them.
4. If media storage location must vary among PCs, one with just drive C:, the other with a second hard drive or network drive that is preferred, there are tricks to give all such locations the same drive letter, therefore the same media storage path. Such as, always store media at m:\media\jrmc\, on every PC. On the PC that has a physical M: drive, just use it.
On the PC that only has drive C:, make it think there is also a drive M:. First make a folder that will pretend to be M:, such as folder c:\mdrive (folder name doesn't matter, but keep it simple). Then use MS-DOS command SUBST something like this: subst m: c:\mdrive. Then put the media files in physical drive c:\mdrive\media\jrmc, but tell MC the files are at m:\media\jrmc, same as the PC that has an actual M: drive.
The beauty is, once the folders and SUBST (if needed) are set up, there's never a need to do anything to the library itself. I've done this for years. Once I set up ALL my media files on drive M: (whether physical or virtual on a given PC), it works great, across a dozen generations of PCs, never had to change the library contents, MC always sees library files and media files at the same location.
NOTICE: My examples points 1, 2 and 3 used drive c: for simplicity, but really, I always use drive m: as explained above.
5. Cover art seems simple but there are many options. Instead of the default location, I tell MC to use a separate folder that contains ALL cover art, on drive M: (physical or virtual), such as m:\media\jrmc\coverart\. I do not embed images in the music files because that makes the files larger (I have a huge library so efficient storage is a consideration. But there are situations where embedding images, or using MCs other cover art options, are desirable. Contemplating and choosing a cover art method is almost a separate field of study within MC.
6. By always having MC's files on the same real/virtual location M:, to copy the entire MC library from Main PC to Secondary PC is simple. I just copy m:media\jrmc to the identical location on the second PC. MC on both PCs is set to use identical paths for everything. All the library files, media files, and cover art files are copied from/to the identical path, so everything works the same on both PCs, nothing to diddle with.
DISCLAIMER: MC is amazingly versatile, with many variations (and contradictions) to the above that also work well. There's rarely only one way, and few will agree on any particular "best" way. Search MC22 and prior forum sections to discover all kinds of advice. So, the best advice is, think first about the result you want, including whatever simplicity vs. flexibility you might require, etc.