[morzh]

Well,

your IF is your RF Input signal minus the Local Oscillator.

So, your IF = |RF - LO|

(that is the absolute value, depending on whether it is hi side or lo side injection).
That is, if your signal 470, then your LO is 940KHz.
How you do that...not sure what they used the procedure for. Using a scope?
usually it is not required.
Once you trim your IF, then the procedure involves setting the oscillator and RF trimmers/padders.