Update README.md

Author: loricrotser

README.md

@@ -16,7 +16,7 @@ Repository Contents
 
 Documentation
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-* **[Hookup Guide](Learn.SparkFun URL)** - Basic hookup guide for the SparkFun Pico Add On Flipper for XRP.
+* **[Hookup Guide](https://docs.sparkfun.com/SparkFun_Pico_Add_On_Flipper/)** - Basic hookup guide for the SparkFun Pico Add On Flipper for XRP.
 * **[SparkFun 3D Model repo](https://github.com/sparkfun/3D_Models)** - 3D models of SparkFun products. 
 
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