You can add a single metric value through the "Add new value" button - just enter the source you are using and set the company, year and value fields. Please follow the methodology for the metric to find out where to look for sources, and how to assess the value a company should receive.
If you have a lot of values to add for a metric, adding these one at a time can be very time-consuming. The import feature allows you to upload a .CSV (comma-seperated-values) file with many metric values all at once. Any simple spreadsheet can be saved as a .CSV file (using software like Excel, OpenOffice Calc or Google Docs). The first step is to add the .CSV file as a source (middle button on 'add source' page, see image below).
The .CSV file you upload should contain two columns: Company and Value - the Company column should contain company names, the Value column should contain the corresponding value for each company.
When you upload a CSV file it becomes a source on WikiRate - please also write a short description of where the data inside the CSV came from, so that people who browse the metric later will know the original source for the values.
When you click submit the source will be created and you will see a page like the one below. Click "Import to metric values" to import the data inside the CSV file as values for a metric.
On the last page you first need to choose the metric which the data relates to, and specify the year which the values relate to (at the moment, all the values in an import must relate to the same year). The rest of this page is about matching the company names in your .CSV file with companies on WikiRate. The check-boxes determine whether the value will be imported, the first column is the name from your .CSV file, the second column is the company entity on WikiRate which we think the value relates to. Please check that these matches are correct, and don't import the value for a company unless you're sure that its being associated with the correct company on WikiRate!