As the other answer explained well (scope connection / ground wrong, and capacitor shorted by solderless breadboard), your schematic should look more like this:

simulate this circuit – Schematic created using CircuitLab
If you run the simulation above, you'll get this plot:

As pictured, the circuit shown has time constant \$\tau\$:
$$\tau = R C = (100 \ \Omega) (1 \ \mu \text{F}) = 100 \ \mu \text{s}$$
The \$V_\text{in}\$ input switching interval, i.e. the half-period of the square wave function generator, is \$t_\text{hp}\$:
$$t_\text{hp} = \frac {1} {2 f} = 500 \ \mu \text{s}$$
The characteristic shape of this RC charging-discharging is determined the number of time constants of settling \$n\$:
$$n = \frac {t_\text{hp}} {\tau}$$
If \$n\$ is large, then the output will look more like the input, with only a brief analog edge. If \$n\$ is small, then the output will look more like relatively small ripple around the long-term average.
With \$n = 5\$, the plot shown here is somewhere in the middle of behaviors. After 5 time constants, the output of the first-order system has settled to within \$e^{-5} = 0.7\%\$ of its final value.