It is very simple to find and install Office 365 Add-Ins!
Simply open one of your Office 365 applications like Word.
Next, click Insert and select Get Add-ins.
A box will appear giving you a number of options. You can then scroll through the complete list of and browse by category or use keywords to search for a particular add-in
You can click on any of the Add-ins to read more about it, including any reviews that may have been posted.
Many of these add-ins are free, but there are an equal number that are related to paid applications that you may or may not already be using. In that instance, the add-in description will advise you that its use may require additional purchase.
Once you are ready to to try out an add-in, simply click the Add button and it will be installed on your computer. Please note though, that if you work in an office where Office 365 is centrally managed by your IT department, you may need t6o ask them to install the add-in for you.