Is compression used in RDS SQLServer database
After you have loaded the data into a table, and as long as you have signed up for a 2016 Standard Edition or above, you can use the Data Compression that is included within Sql Server:

CREATE TABLE t1
(
    ... -- whatever columns you need.
)
WITH 
(
    DATA_COMPRESSION=PAGE
);


You can also create compressed indexes in a similar fashion:

CREATE INDEX idx_t1 ON t1(...) WITH (DATA_COMPRESSION=PAGE);


For more information, check out the documentation for Enabling Compression on a a Table or Index.