Do you want to display FPS on screen when you're in the game.
By default there "FPS" showing in Elden ring game you will be manually enable this feature if you want show "FPS" on game screen.
To "Display FPS in Elden Ring" Opne Stem App in computer and tap on stem in the top left corner.
New pop-up will be open with you where you will be find settings tap on it.
Next go to In-Game next got to In-game FPS counter tap on "arrow icon" and select the left corner after that restart the game and the fps will be show on the main screen of the game.
Here's how to "show FPS" in Elden Ring:
1. Open "Steam"
The first thing to do is open steam on computer.
To do so, Navigate the "steam" in you're system and open it.
2. Go to "Settings"

After you "Open steam" then next you need to open settings in steam.
To do so, "tap on steam" in the top left corner and new pop-up will be open with you where you will be seeing "change account", "Go offline", "cheak the steam update" etc...
Find the settings in the pop-up and tap on it.
3. Tap on "In-Game"

After you tap on "settings" next you need to enable the display option for FPS.
To do so, Tap on IN-Game in the left "menu".
Once you Tap on "In-Game" new window will be open with you there locate the In-game FPS counter below overlay shortcut keys.
4. Select "top left"
Once you come to "In-Game" Window scroll down and find the In-game counter section its next to "Overlay shortcut keys".
Once you locate the "In-game counter" next tap on arrow icon in box where new pop-up will be open with you.
Then "select" the desired place that you want to show the FPS on screen during game.
After that restart the "steam" and relaunch the Elden ring game and the FPS will be display on you're screen.
How to show FPS in Xbox Game Bar Overlay

If you prefer to use a more detailed FPS counter, which will in addition show your CPU and GPU utilisation as well as your VRAM and RAM usage, then you should consider using the integrated Xbox game mode overlay.
To do so simply type window key & G in keyboard and pin it to you're desired location in you're system.
Conclusion
To "Show FPS in Elden Ring in Game screen" you will be manually enable this feature then you can do it.
To enable this feature go to settings in steam and search for In-game then Go to "In-Game counter" and select the desired location in you're system and the FPS will be show on you're screen.
Alternatively if you want to show the FPS on XBOX simply type Window key & G and pin to you're system.