Wire one fan on constantly

Hi lads and ladies , finally got the legacy back to gether after waiting six weeks for a bottom hose from Subaru, still making sure its bleed properly, but when I was in Halfords getting coolant the guy said he had a scubby and had one of the fans running constant to avoid over heating.Q how do I do this. Any other tips welcome

again thats not needed if car has no issues.

Don't believe everything you here in halfords

As above no need