This is the lower harness for the S14 SR20DET as reference. Check the actual wire on your S13.
E201-203: these connectors have the wires that you need to mate to the body harness. You may be able to just plug them in or you may have to cut the connectors off and redo the wiring yourself. This depends on the year and options on the shell. Since there are too many variations in the body harness, I can't cover them all. Just know that any wire you need to connect to the body harness will be done at these plugs as indicated below.
E204: 1 ring terminal. White. Connect to the battery positive terminal. Keep in mind that sometimes JDM battery terminals are smaller and you may have to enlarge the terminal. You can clip the terminal off and get a custom terminal with the right size at your local auto parts store.
E205: 1 ring terminal. White. Main power. Connect to the 75A or 100A fusible link at the underhood fusebox. Look at where the stock lower harness bolts to. This is where you bolt the E205 connector. Make sure that you bolt this opposite of the battery on the 75/100A main fusible link. The SR ring may need to be enlarged in some cases to fit the body.
E206: 1 ring terminal. Black. This is the ground wire for the alternator. Connect this ring terminal to the bolt behind the underhood relay box.
E207: 3 connectors:
1) Large insulated ring terminal. White. Connect to the large stud on the alternator. This wire goes to E205.
2) Small ring terminal. Black. Connect to the small stud on the alternator. This wire goes to E206.
3) Large 2pin connector. Connect to the alternator.
White: fused constant power. This wire goes to E205.
White/Red: CHARGE warning lamp in the gauge cluster. Not needed. This wire is connected to the E201-203 connectors. Verify continuity as needed and connect to the correct wire on the body. Otherwise this is not needed to make the engine run.
E208: Unknown connector and colours. This is for the EGR. Wires are connected to E201-203. Not needed.
E209: large black plug. Yellow/White. Not needed. Check the E201-203 connectors for continuity and connect to the OIL light if needed, but not necessary to run the engine.
E210: black 1pin. Black/Yellow. Connect to the starter solenoid. Check the E201-203 connector for continuity, and connect to the starter solenoid signal on the body.
E211: 2wire grey connector. Yellow/Black and Yellow/Blue. Vehicle Speed Sensor. Not needed. Otherwise check continuity at the E201-203 connectors and hook up to the VSS circuit on the body. It doesn't matter which wires get connected to which on the body. Current can flow either way through the switch. Not need to make the engine run.
E212: 2wire grey connector. Green/Blue and Green/White. Reverse lights. Not needed. Otherwise check continuity at the E201-203 connectors and hook up to the reverse light circuit on the body. It doesn't matter which wires get connected to which on the body. Current can flow either way through the switch. Not need to make the engine run.
E213: 2wire grey connector. Unknown wires. Neutral switch. Not needed.