How to use spi to write and read some specfic register address

I think @AkosLukacs has hit it on the head. SPI should be pretty straight forward. The main gotchas are:

• The register is usually sent as the first byte
  
• When you read, you need to send the register and then another byte (usually 0 or 255). The first byte you get back is then basically garbage and what comes after is the data.
  
• Often devices set the top bit of the register to indicate a read or write (so reg|0x80 - the code above uses 0xC0 which I think is specific to the LIS2DH12. You'd have to check your chip's datasheet.
  
  

If you post the code you have up here we might be able to help you a bit more.