Solution 1 :

Assuming you have opened the firewall port 1521 to the RDS server, you should be able to use sqlplus, sqlci, sqlldr to connect to the RDS instance as follows:

USER/PASSWORD@//hostName:port/SID

e.g.

sqlplus scott/tigerD@//myhost.this.that.amazon.com:1521/THE_SID

Once you prove this works, use this in the tools to squirt data into the RDS instance.

E.g. .sql INSERT scripts, sqlldr scripts etc.