Ok, a consult with an accountant would explain this better and in more detail but in brief :-
1) The RCTDC is provided by a principal contractor to a "non-C2 holding" sub-contractor. Tax at 35% is deducted from the sub-contractors payment and remitted by the principal contractor to Revenue.
2) The sub-contractor may apply to Revenue for refund of some-all of the tax depending on their tax affair situation. Alternatively they may wish to have Revenue hold it against their year end tax/PRSI bill.
3) The sub-contractor is self-employed and must account for their own taxes so registration with Revenue on form TR1 is necessary. This may, depending on the level of income also bring the sub-contractor into VAT
4) The sub-contractor, if in a continuing contract , may apply for a C2 in which case the principal contractor no longer has to deduct the tax. To do this the sub-contractor needs a contract with a principal contractor ( a letter from the principal with the C2 application is usually needed) and 3 year clear tax history ( being on PAYE would satisfy this )
As said at start, if this is going to be ongoing, I'd recommend you talk with an accountant.