How do i index a CLOB column in oracle

I have an database table that contain one column that holds a numeric data type. Rest of the columns are CLOB columns.

I am in the processing of migrating the contents of this table into the new database schema which i developed. Since my migration script are written in ASP.net, it is taking a lot of time to load the table and it time off everytime.

Any advise or experience in the relavant field.