There's plenty of open-source information on the basic call for fire - such as
061-283-6003 (SL2) - Adjust Indirect Fire
The process will be taught before you need it, and checklists should be provided to ensure you know the sequence. To best prepare, it might be better at this point to focus on the fundamentals:
Map using
- identifying your own location
- identifying a distance location with similar accuracy (e.g., a target)
Determining Direction
- from you to a given point (e.g., a target)
- by use of a compass
- by use of the map
Judging Distance
- from your location to a distance location (e.g., a target)
- between two distant locations, roughly in line with one another (e.g., the range between an adjusting round and the a target)
Math
- the WORM rule (which is used to calculate the correction left or right to bring the adjusting fire onto the observer-target line)
These elements are where many people first attempting to adjust fire in practice, whether on a live range or simulation, tend to fail. The basic proforma for the call for fire isn't challenging, but the underlying skills to provide accurate data rapidly can be for some.