Antidote (see here for details) is a powerful French language grammar checker. It provides error analysis, grammar diagnostics, an online dictionary, and much more. It is installed on all of the computers in the Kingston Hall semi-public site and can run either standalone or within Microsoft Word. We will describe the version within Word here.
Let's assume you typed this:
To check this, click on the Antidote tab:
Then click on the Correcteur button. When you click on this button, Antidote will create a new page to correct your text. This page is dynamic: it will transfer your corrections back to your original text in Word. The reverse is also true: as long as both pages are open, changes to your original text will be sent up to the correction page. For example, if you encounter a complex situation on the correction page, you can go down to the level of your original text to revise the sentence and then go back up to the correction level to see if your revisions are acceptable.
An Antidote window will open that looks something like this, where you are given the choice of correcting the first error, where Ce has been used in place of Cette:
If you click on the Green check mark, the error will be corrected and you will see this:
The question mark beside paume means that Antidote isn't sure about this. In this case, since pomme is the correct form, click on the right-facing triangle to go to the next word. You will then see this:
Continue in the same way for each possible error until your text is correct, as in:
You can then save your text.
Remember, however, that Antidote is just a piece of software and not a human. It can be dumb and give inaccurate diagnoses. It's up to you to use your judgement when using it. However, it does do a very good job of catching things that humans miss.
You should note also that Antidote includes a built-in dictionary that you can access by clicking on Dictionnaires. An example of what is contains is shown below:
If you want a more basic grammar checker, you can use the one built into Microsoft Word. Instructions for using it can be found here.