The instrument rating allows you to operate an aircraft for which you have a rating in IMC conditions or under IFR. Most pilots would do an IFR in conjunction with their CPL.
Requirements to obtain a Instrument Rating
1.Private Pilots license or Commercial pilots licence
2.Class 1 Medical
3.20 Hours Dual training on an approved simulator
4.20 Hours Instrument training on an aircraft
5.A practical test done with a SACAA approved DE.