Configuring Synapse:

You may use the sample config located at %%ETCDIR%% to get started. It
already is configured to find the configuration in that location and
places the database in %%DBDIR%% and the logs in %%LOGDIR%%, but there
are some crucial values you will need to populate with unique data:
registration_shared_secret and macaroon_secret_key. Both of these
by default are 50 character random strings. These are by default set to
CHANGEME_50CHAR_RANDOM in the sample homeserver.yaml.

If you wish to have Synapse handle this for you including generation of
self-signed TLS certificates and dhparams you can use the following
command:

%%PYTHON_CMD%% -B -m synapse.app.homeserver -c %%ETCDIR%%/homeserver.yaml --generate-config --server-name=example.com

Please note that you will still need to manually configure paths to log
directory, database, and media storage with this method.

It is also important that you deploy a TLS certificate that your
clients accept as valid or some functionality will fail to work
correctly (eg, media file retrieval).