Hi Tom,
Assuming as you may be know the ETL concept. once we loaded the SRM Data into bw targets then we can do the report by using bex tools(query designer).
Based on your requirement first we need to find related data source. Take functional team help and find the technical specs.
Once you know technical specs,
1. You can find available standard data source form business content.
2. if you have standard data source then just activate data source form TX - RSA5(SRM) and do the require maintenance at RSA6(SRM).
3. You can cross check about your data source extraction Tx - RSA3.
4. Later you can replicate srm data source into bw system.
5. Activate your data source
6. you install business content info cube,info pack/transformations/dtp if available.
7. take srm info cube, install form business content, you groping option as dataflow before. you will get all( point 6).
8. Once data flow was designed, load the data and do the reporting.
if you don't have standard data source as per your requirement, based on SRM Tables try create generic data source by using RSO2.
Generic data source concept may be know to you.
Thanks