Are you telling the truth there, or has a naming confusion crept in already? - I mean, what else do you have, because just a Raspberry Pi and emonCMS is not enough - you need something to measure the power/energy in the first place.
Is this thread relevant Emon system tips for absolute beginners? or is that a different system?
Is there any reason to suspect it does not have the operating system as well? If you bought the SD card from the OEM shop, it will be the OS plus emonCMS.
Other than the Guide, no. If you do look at the guide, you have effectively got an emonBase, but (as you didn’t mention anything other than a RPi) without the radio module, so you won’t get data from an emonTx or emonTH via that route.
Fire up a web browser and look at your router to see which devices are connected to your LAN.
Put the SD Card into the card slot in the RPi, connect the power and wait for it to start up.
Check your router again. You should see a new device - your RPi. Look at the “Dotted IP Address” that the router has given it (something like 192.168.1.74) and go to that address with your browser. You should see either the emonCMS set-up page or the emonCMS login page. The first time, you will need to set up your account name for emonCMS and invent a password (these are only for emonCMS itself). Take care to record both somewhere safe, because resetting them is painful.
{I always connect first time via Ethernet direct to the router - I find that’s a lot more straightforward than via the Wi-Fi method}
DON’T pull the power on your RPi - always (whenever possible) do a graceful shut-down via the Admin menu, or you risk a corrupted SD card.