After downloading solidworks by following the link of one of your technicians the software was in English, a secretary described to me a procedure for changing the language which consisted of putting the language of the PC in French France (I am resident in Switzerland) then to modify the program and do the following, The software looked for updates and then validated the installation but it remained in English.
To complete @dbz, I don't remember choosing the language during the installation. In which case you have to uninstall and reinstall SW (maybe a simple repair, accessible via the add/remove program menu would be enough).