This means that you will* receive a tax credit up to a maximum of €3,175@20% = €635 per annum. If your fees are say, €3,000, the tax credit will be €3,000@20% = €600 per annum. You should receive a statement of tax credits from the Revenue every January/February. I'm not sure if fees can be claimed in the year they are paid or in arrears.
Oh yeah, I presume that you will have paid tax to use this credit against? I'm not sure what the position is if you are not earning any income, but are receiving tax credits (i.e. do you get a cheque from the Revenue or is the relief carried forward)?
*Presuming the course you take qualifies, I'm not sure that all do. Best to contact the Revenue directly.