I wish to use French words in an article which need accents.
Which keyboard layout do you use? For example, the US-International layout uses dead keys to insert accents and other special characters. LibreOffice also offers autocorrect options to substitute combination of characters, but IMO using an appropriate keyboard layout is always the best solution.
The problem with language keyboard layout is key output no longer corresponds to the physical key engravings. If, like me, you’re not a professional typist (in the target language), you may be relying on the labels on the keyboard.
As a consequence, I prefer to customise my keyboard to add “dead keys” (active accents) on keys which I associate with my use of the accent (think, for instance, of the tilde I’d put on the N key because it is its major use in Spanish). This can be quite easy on some OSes.
To answer the initial question, look at the numeric row on your keyboard. Generally, the accents may already be hidden there with Alt Gr and optionally Shift key. Not very intuitive.
If you are only occasionally using French words, and if you are using Windows (you didn’t say which OS), there is a character map in Control Panel (Windows 7) which is very useful, for inserting accented Latin letters into your document and for all sorts of mathematical and typographic symbols. For easy access, create a shortcut to it on your desktop.
Following the same idea, but OS-independent, you can Insert>Special Characters.
You will find quite a lot of information on similar questions, for example
How do I add French accent marks ( á, à, è, é, û, ù, etc.)? and
Shortcuts for french accents on qwerty keyboards?
but the following brief notes may also help.
The keyboard is controlled by the operating system and there is usually a command such as KEYBOARD on my linux-mint system. this command will normally give you a keyboard layout for you to examine and print.
The English (UK) International and English (USA) keyboard layouts are NOT the same, especially the Alt/Gr keys, so make certain you use the correct version.
There are four main text levels on a standard PC keyboard called level 1-4. 1 is lowercase, Level 2 is uppercase, level 3 is Alt-Gr lowercase and level 4 is Uppercase Alt-Gr. So for example on my keyboard the four levels will give for c: c C ç Ç, and e: e E é É, a: a A á Á, s: s S ß §, 4: 4 $ € ¼ etc.
The € (EURO) key varies from system to system. The keyboard command usually gives you an option to change it to suite your requirements.