On Safari, open the page with KML files and click on the file you want to upload.
Open Files app, navigate to Downloads folder, press on the file you just downloaded.
In the top right corner, press on the forward button
You should have Foreflight icon present in the list, press on it.
If you use Chrome, it is even simpler. Press on the KML file you want to upload.
Press on the Download and the bottom on the screen.
When download is completed, press on Open in....
Similar list of applications should be present.
After you selected Foreflight, the app will open, select Custom Content
Select Custom Map Layers
Press OK after the file was imported.
Go to Maps tab and press on the Layers button at the top of the screen
MVA altitudes will be displayed on the map.