Recommend Website for uart or spi

what is a good website or book to learn how to program wth UART OR SPI? i have 0 knowledge about them and cant seem to find much information about them. thanks

Try the Arduino main site. Collect bookmarks as you browse.

UART --- Arduino IDE has the Serial library (included when Serial.begin() is coded) for those.

SPI --- Arduino has an SPI library that must be #included but you have it.

Your Arduino IDE has not just the libraries but the library examples to work with.

Your Arduino IDE has Tutorial Examples to work with, go through sections 1,2,3 and 5. SKIP section 4 unless you like to learn bad habits (use of capital-S String) and eventually need to learn C lowercase-s strings.

The main site has a page named Getting Started that points these things out, but that's reading written directions.. sort of like this post only longer with more info.