Doing PCA and ICA analysis on EEG data with 24 channels
First of all, I would recommend working with a domain specific (EEG) and established analysis package of your choice. You mentioned python, so I would advise you to check out MNE-Python. There is a tutorial regarding eyeblink detection/correction/rejection from EEG data that you could work through.

To answer your general question, ICA and PCA are typically done on the complete data matrix, i.e., each row of the data matrix is a channel and each column is a sampled timepoint (values in microvolts).