45+ can go directly to centres, they'll register them at the centre, if they didn't registered themselves on Cowin, they just need to carry identity proof with them.
For people of age grout 18-45, they'll have to register themselves at Cowin or ArogyaSetu, and put identity proof details (same identity proof should be carried from which they've registered to their allocated centre ) they'll get a slot available in there region and then they'll have to choose their time period in which they'll prefer to come. This is to avoid unnecessary crowd near centres, that's why 18-45 has to register before they go to these centres.
Some states are going to give vaccines free to 18-45 group, though paid ones are available too.
I haven't registered myself successfully, but I think so people can see which vaccine is available at which centre, and they can choose those centres too.
12