Follow step 1 of Apollo Router quickstart to download and run the router.
Your execution should like look this to run the router against your lynx supergraph after downloading the router.
APOLLO_KEY='service:lynx-n321j:xxxxxxxxxxxxxxxxxxxxxx' \
APOLLO_GRAPH_REF="lynx-n321j@current" \
./router
This results in the supergraph running in the router locally with a GraphQL endpoint of:
http://localhost:4000
If you encounter errors when executing queries, you may find it useful to configure the router to include subgraph errors. To enable this within the router, follow the instructions here.