JSTOR is a very popular general use database which provides full text searches of almost 2,000 journals, and many full books as well. Although you can find materials covering a wide range of topics, JSTOR is typically best for finding literary criticism and reviews.
The JSTOR home page looks a lot like Google with a single easy search bar in the middle. By default, keywords will search all text. By clicking the "Advanced Search" link below the main search bar, you can find other options, such as title searches or author searches which can be selected from drop-down menus (as shown below) and allow you to search for your keywords appearing in only the title, or only by a particular author. You can add additional search fields by clicking the "Add Field +" button below the initial search boxes. If you want to exclude certain terms from your search, you can also use the drop-down menu on the left-hand side of each search bar to "NOT" which will indicate you want results that do not include a given term. JSTOR also defaults to "Read and download" as the access type, meaning that the results of your search should be available in full text.
There are also a few other advanced search options that you can take advantage of when using JSTOR. Just below the search fields you will find a list of options under the heading "Narrow By," which allow you to apply search filters to get more specific kinds of results. These include limiting your results to "Articles" under "Item Type" (which will generally help to return only scholarly articles in your search), as well as limiting to certain date ranges (a common requirement from professors being using only the most recent research).
You can also refine your search results in a few different ways once you have made an initial search. The most common ways will be to click the "Modify Search" link as highlighted below, which will allow you to change the parameters of your existing search. Another options is to check the "Search within results" box and simply add new terms to the search bar at the top of the screen, which will search for the new keywords only within the results you have already generated.
Once you find a particular item that looks good to you, you can click on the blue title link to open the article's record. You can also click on the author's name from the main list of results to see what else they have published. Within an individual article's record you can view and download the article itself, browse all of the references listed within that article, find all of the metadata that you need to create a citation, or even click a simple button to auto-generate a citation for you in a few of the most common formats (MLA, APA, and Chicago) -- though you should always make sure that this citation is pulling the correct information! It's a great tool, but always double-check.