The mltypemap utlity comes with elaborate documentation the should give you all the information you'll need to get started. Using the cdnshelp utility, please look for Universal Verification Methodology->UVM Multi-Language Reference->6. mltypemap utllity.
Basically, you give irun all the input files you need for compilation as usual, and provide a TCL command file containing instructions specific to mltypemap on how to map the needed types. For example. assume you have an e file foo.e that contains struct 'my_pkg::bar' that you want to map to SV. Your TCL file can look like:
// TCL file for mapping e type to SV
maptypes -from_type e:my_pkg::bar -base_name base -to_lang sv
And the irun command:
irun foo.e -nosncomp -mltypemap_input do_map.tcl
Please lt me know if you require additional information.