I googled 'ECCSIM' to find out what on earth it is. I now have some idea, even if I am not 100% certaiin what a 'perfusionist' is, but I gather it is a simulator for training the operators of things like dialysis machines.
I did NOT go and download the software - at least in part because I have no interest in the field - but the couple of web-sites I looked at suggest it is perhaps not in finalised form, possibly a 'beta' version.
However, if the installer is a normal .exe or .msi type, the normal procedure would be to download the file to some location where you can find it, then run it to install the application. There are at least two ways to do this. If you have the 'Run' command on your Start menu, click 'Run', click 'Browse', browse to wherever you saved the file, select it, click 'OK', click 'Run' and the installer should start running. You will have the normal UAC screen to get past before it starts to run.
The other way is to open 'Windows Explorer', browse to where you saved the file, and double click on it. This will usually start it running. You will again meet the UAC screen.
You may then be asked where you want the installation to go. the normal choices are 'Program Files' for 32 bit software and 'Program Files (x86)' for 64 bit software. From that point on, the installation should proceed automatically and come up with a message saying 'Finished' or words to that effect.
If the installer is a 'beta' as well, ie not a fully de-bugged market ready product, it may not install everything where it should go ! In which case you may have to move some files yourself.
If you can find this file 'MSSTDFMT.DLL' using Windows Explorer, then you can move it to the 'Windows\System 32 folder' by either 'Copy / Paste' or 'Cut / Paste' or by using 'Drag and drop'. If all of this is taking place on the same hard drive, then 'Drag and drop' and 'Cut / Paste' are identical in their effects - you move the file from one place to another. 'Copy / Paste' leaves a copy of the file in its original position.
I have never heard of 'running' or 'executing' a .dll file, but they usually need to be in the correct place and the System 32 folder is as likely a place as any.
I think, and only think, that your friend means that you should ensure the this fiile is in the System 32 folder, and then try running the application again.
I hope this provides some clarification, but the author's web-site - which I think is a Japanese University - may provide more info.
Louis has just made a reply to this, which you may well wish to heed !