This is how I do them (other more correct ways probably available but it works for me!).
As Mick above says, use a pin hammer (aka a small headed hammer). Put the rivet with it's head down on a suitable surface, lay the metal parts over that are to be riveted together, then get a piece of paper, I use post it notes, and press it over the end of the rivet so the end pokes through. Two purposes for this - firstly so you can rip it off later so there is a small amount of play, and secondly, the paper holds the assembly in place while you tap it with the hammer.
An example of a pin hammer - https://www.amazon.co.uk/Amtech-A1100-Lightweight-Dropforged-Hammer/dp/B004QDU35Y/ref=asc_df_B004QDU35Y/