To create a GEDCOM file from GRAMPS, choose Export... from the File menu. A popup box gives you an overview, click Next to continue.
You can now choose the format of the export file. You need to use GEDCOM to transfer to WeRelate, once this is selected click Next to continue to Export options.
On the Export options page you can select 1 to exclude private records 2 to exclude living people (you do not have to exclude them from the GEDCOM but they will be excluded by the importer.) The person filter 3 automatically selects the currently active person and you can chose from a number of inbuilt filters or if you have created your own filters you can choose one of those. The calculate preview will show the number of people that will be included in the GEDCOM, once you are satisfied click Next to continue.
You can now name the file and choose where to save it, the default .../gramps/backup is probably good. The next page confirms your choices and you can select Apply to save.