This is what the help on icustom says:

double iCustom( string symbol, int timeframe, string name, ..., int mode, int shift)
Calculates the specified custom indicator and returns its value. The custom indicator must be compiled (*.EX4 file) and be in the terminal_directory\experts\indicators directory.
Parameters:
symbol - Symbol the data of which should be used to calculate indicator. NULL means current symbol.
timeframe - Timeframe. It can be any of Timeframe enumeration values. 0 means the current chart timeframe.
name - Custom indicator compiled program name.
... - Parameters set (if necessary). The passed parameters and their order must correspond with the desclaration order and the type of extern variables of the custom indicator.
mode - Line index. Can be from 0 to 7 and must correspond with the index used by one of SetIndexBuffer functions.
shift - Index of the value taken from the indicator buffer (shift relative to the current bar the given amount of periods ago).

Sample:
double val=iCustom(NULL, 0, "SampleInd",13,1,0);

13 = input required
1 = the 2nd Buffer is being called (use 0 if you want the first buffer)
0 = current bar

for the ifisher

it should be something like this

double val=iCustom(NULL,0,"iFish",0,0);

As there is no input required, that entry is skipped.

Hope this helps.