Depends.
1. Determine if you need caravel (only digital pins available and some 150 ohm terminated analog pins) OR caravan (which has analog + noesd pins)
2. Design your analog circuit.
Then two variant exist. Using manual and digital flow.
1. Manually place and connect the macro inside caravan wrapper <- simple
2. Pass the LVS/DRC/PEX/Simulation
3. Pass the precheck
Second variant if you need digital components, then you need to use OpenLane.
1. Make the LEF
2. Make verilog wrapper
3. Make verilog netlist/RTL
4. Configure OpenLane
a. May need placement and even adding blockages for analog routing as OpenLane uses digital routing rules and buffers on analog nets
5. Same: pass LVS/DRC, but PEX/Simulation might not be reasonable