Adding_voltages_and_ current

Hi!! ...

My question is that, how do I, practically, add:
(i) voltage from two or more sources (e.g. v1 from a battery source, v2 from another
battery source, v3 from a small solar power unit (dc), ....... (etc., etc.)

(ii) Current from two or more sources (e.g. I1 from a battery source, I2 from another
battery source, I3 from a small solar power unit (dc), ....... (etc., etc.)

The above two cases are required for either AC or DC power sources respectively, as per 'series' and 'parallel' arrangements for the above. I am grateful and thankfull in advance to whome answering my above question the soonest please.

smartmachine_101@yahoo.com