I agree the implementation of the IOMUX is confusing at first acquaintance, and it's not helped by missing or incomplete documentation.
To start I found it easiest to look at some SDK example projects, I've not used RT1010 but if it's the same as RT106x then you should see calls to IOMUXC_SetPinMux() that sets the pin muxing and IOMUXC_SetPinConfig() that sets the pin config.
Also looking at the contents of fsl_iomuxc.h can be a quick way to see which muxing options are available for a given pin, and you can use the pin function ID's to quickly configure the pin.
-Nick