Dole
Anyone can sign on at their local Employment Exchange, provided they are unemployed, either fully or partly. There used to be a facility where self-employed people could sign weekly and indicate which days of the previous week they had been working. Payment for these days would then be deducted from their weekly entitlement.
If you have ceased to be self-employed completely, you can of course sign on in the normal way. You should make the claim from your first day of unemployment as it unlikely that a claim will be back-dated to when you say you were unemployed. The payment you receive will depend on your PRSI payment history. To qualify for unemployment BENEFIT you would need to have made a minimum number of PRSI contributions in a particular tax year (at present, I think this would be 2002 - from 1 January, this is likely to change to 2003, etc). If you have paid these contributons and if you satisfy the other conditions (available for and seeking work, etc), you would be entitled to an automatic payment which varies according to the number of dependants you have.
If you have not made sufficient contributions in the given year, you may still be entitled to unemployment ASSISTANCE. This is means-tested and will take into account your persoanl and financial circumstances such as alternative income, savings, outgoings etc.
Even if you don't qualify for either form of payment, it may still be in your interest to sign on for CREDITS. While this would not involve payment, it would help to keep your PRSI record in order which may be of benefit should you ever seek a state-pension. Your local Social Welfare office could advise you on this.