Are you using a traefik.toml file mounted from a Kubernetes ConfigMap ? If yes, then edit the configmap to specify the filePath directive(s) ([traefikLog] -> filePath and [accessLog] filePath) and restart Traefik's pod so it takes the change in account. Corresponding documentation for Traefik v1.7: https://docs.traefik.io/v1.7/configuration/logs/#toml
Are you using command line (e.g. "CLI") parameters in the Traefik Deployment ? Then add the flags --accessLog.filePath="/path/to/access.log" and --traefikLog.filePath="/path/to/traefik.log", apply it, it will re-create a pod with these changes. Corresponding documentation for 1.7: https://docs.traefik.io/v1.7/configuration/logs/#cli
IMPORTANT: the link you posted is for the latest version of Traefik, which is v2.0. Be careful to use the v1.7 with the left-bottom drop down menu (last of the Table of Content).