FOAF is an RDF vocabulary for describing basic information about people and their relationships to other people. It is a fairly popular vocabulary; many people, when they get started with RDF, create a FOAF profile, which is an RDF graph that uses FOAF to describe themselves. This document instructs you in creating your own FOAF document, in order to help you understand how to use Rej.
To begin, install and start Rej. Create a new working graph using File → New (or Ctrl+N). We will be making statements in the FOAF vocabulary, so you will need to download a copy of the FOAF schema, then load this file as a context graph in Rej using File → Load context.... Mainly, you will be making statements about yourself, so you need a resource URI for yourself. In my case, I chose tag:jlc6@po.cwru.edu,2005:self. Expose your chosen URI with Edit → New resource... (or Ctrl+R), then mark this resource using Edit → Mark (or Ctrl+M), which will cause it to be the subject of future statements (until a new resource is marked).
Now let's record our name. I suggest using the foaf:name property for this, so we need to find and select this property, then actually make the statement (or triple) using this property. To find the property, use Tools → Search (or Ctrl+F), enter "name" and choose OK. Choose "name" from the Resources pane by double-clicking on it (or pressing Enter while it is highlighted). This shows details for this resource in the Current resource details pane, and, because it is a property, also moves this resource to the top of the Properties pane. We can inspect the details of this property, and, if it is the property that we want, we can use it to make a new statement about the marked resource.
To create the new statement, select the "name" property from the Properties pane, then choose Edit → Make statement with new object... (or o) and type in your name. Leave Literal value selected, as this property takes a literal object, then choose OK. The marked resource has been updated with the new label, and a (+1) tag indicating that 1 new statement has been made about this resource since it was last viewed in the details pane.
We also want to say that the current resource is a person (using foaf:Person). Find both the rdfs:type property and the foaf:Person class, and bring them to the top. Display the foaf:Person class in the details pane (to make it the object of the statement), select the rdfs:type property from the Properties pane, then choose Edit → Make statement (or s) to create the statement.
FOAF has many other interesting properties and classes that you can use to enrich your personal profile, such as foaf:mbox and foaf:mbox_sha1sum for identifying your email accounts, foaf:homepage for linking to your homepage, foaf:knows for linking to other people you know, and many others. In addition, you can bring in other vocabularies to further annotate your profile.
To view the statements directly related to your marked resource, search for that resource and then choose it from the Resources pane. To save your new FOAF profile, choose File → Save (or Ctrl+S).