Oldie but Newbie

Hi all,
Living in Cambridge England,
Hoping to enter a local Olympic tri in the summer as a fundraiser. Previously a road cyclist but running is hard on my old joints. Swimming is coming along after stripping it back to basics and working on form.

I currently work shifts so find it difficult to train with a local club as I prefer to be home with my partner at weekends.

Any tips would be most helpful
Ps, just enrolled on a sports nutrition course hoping to enlighten myself ( love chocolate)