First make sure that you have tendermint core.
Then run tendermint unsafe_reset_all to reset the tendermint node. Make sure that you have backed up any relevant data in ~/.tendermint.
From here start the abci app by switching into the example directory with cd example and running npm start.
Now start the tendermint node with tendermint node.
It this point you should be able to interact with your blockchain and its app.
Go to http://localhost:46657/ to see all available endpoints.