add sync doc to readme

README.md

@@ -216,12 +216,7 @@ DB_DSN=bbgo.sqlite3
 
 Once you have your database configured, you can sync your own trading data from the exchange.
 
-To sync your own trade data:
-
-```sh
-bbgo sync --session max
-bbgo sync --session binance
-```
+See [Configure Sync For Private Trading Data](./doc/configuration/sync.md)
 
 ## Using Redis to keep persistence between BBGO sessions
 

doc/configuration/sync.md

@@ -0,0 +1,33 @@
+# Sync Private Trading Data
+
+You can use the following configuration (add this to your bbgo.yaml) to sync your private trading data, like closed orders and trades:
+
+```yaml
+sync:
+  # since is the date you want to start sync
+  since: 2019-11-01
+  
+  # if you have multiple sessions defined, but you don't want to sync all sessions, you can define a list here
+  sessions:
+  - binance
+  - max
+  
+  # symbols is the symbol you want to sync
+  # If not defined, BBGO will try to guess your symbols by your existing account balances
+  symbols:
+  - BTCUSDT
+  - ETHUSDT
+  - LINKUSDT
+```
+
+Then you can start syncing by running the following command:
+
+```shell
+bbgo sync --config config/bbgo.yaml
+```
+
+Or just (if you have bbgo.yaml is the current working directory):
+
+```shell
+bbgo sync
+```