Use sampctl!
sampctl package install pawn-lang/YSI-Includes@5.x
Download the latest version of the library and its dependencies from:
https://github.com/pawn-lang/YSI-Includes/releases/download/nightly/YSI-Includes-nightly.zip
And extract the contents of the contained YSI-Includes directory to pawno/includes/.
YSI shows a lot of information when it starts up, and does some things that aren't necessary in every script. You can disable a lot of these with the following defines:
// Don't display the message about caching the code (with `YSI_YES_MODE_CACHE`).
#define YSI_NO_CACHE_MESSAGE
// Don't display the message about startup optimisation (it still happens, you just aren't told).
#define YSI_NO_OPTIMISATION_MESSAGE
// Don't check if this is the latest version of YSI.
#define YSI_NO_VERSION_CHECK
// If there are no filterscripts also using YSI.
#define YSI_NO_MASTER
#include <YSI_Group\y_library>