instantiating sopc block in top level vhdl file

The same as any other block

i.e block declaration is:

COMPONENT sopc_block IS 
    PORT
    (
...
        this_is_an_input_conduit_end :  IN  STD_LOGIC;
...
);
END COMPONENT

Instantiation in a top levelis:

ENTITY top_level_hdl IS
PORT (
...
   top_level_signal : IN_STD_LOGIC;
...
);
sopc_inst : sopc_block 
PORT MAP(
...
   this_is_an_input_conduit_end =>top_level_signal,
...
);

If you want a complete example you can connect your sopc block in a top level schematic, then use Quartus to automatically generate the VHDL file, so you can see how to fully instantiate the block.

Regards