You first need to select United Kingdom Extended keyboard from the Clock, Language and Region on Control Panel (or the modern equivalent). You can then select appropriate accents for French: grave is top left key next to number 1 followed by the character; accute is alt gr + character; cedilla is alt gr + character; ^ is alt gr + ^ followed by character; " is alt gr + " followed by character. I think there are some others. I hope this helps.