1 - install PSO
2 - remplace the pso.exe by one of the pso.exe aviable at the download section.
3 - run the game
Official address for the pc server : gsproduc.ath.cx

Howto for DreamCast :

Connecting to the server with a DreamCast is a litle bit more hard that PC version. Here is the CodeBreaker code for eatch PSO version on DreamCast, just apply the correct code to your game.
Note : those code is for CodeBreaker only.
Official address for the pc server : pso-dc.ath.cx
US V1, JP V1, EU V1, JP V2, US V2, EU V2

US v1 Server Connect
0E083CA4
0001002C
012866FA
00007370
022866FC
63642D6F
02286700
6874612E
02286704
0078632E

PSO JP V1

JP v1 Enable Code
1D679724
C0705040

JP v1 Server Connect
0E082184
0001002C
0128CC1A
00007370
0228CC1C
63642D6F
0228CC20
6874612E
0228CC24
0078632E

PSO EU V1

EU v1 Enable
144F9758
C0705040

EU v1 Server Connect
0E083C20
0001002C
012861CA
00007370
022861CC
63642D6F
022861D0
6874612E
022861D4
0078632E

PSO JP V2

JP v2 Enable Code
116F90D5
C0705040
19C7D212
40707044
1D2C10FE
0000D003
1D34D0FE
20119102
1D44D0FE
0009000B
1D54D0FE
00008133
1D64D0FE
AC937978

JP v2 Server Code
0E0AADCC
0001002C
002EC50B
00000070
022EC50C
642D6F73
022EC510
74612E63
022EC514
78632E68
022EC518
00000000

PSO US V2

US v2 Enable Code
1B7AAF61
8C5FF000
116F90D5
C0705040
1A87D212
40707044
1EEC10FE
0000D002
1EF4D0FE
2012D102
1E04D0FE
0009000B
1E14D0FE
AC9382C8
1E24D0FE
C74849AE

US v2 Server Code
0E0AD788
0001002C
002EEA73
00000070
022EEA74
642D6F73
022EEA78
74612E63
022EEA7C
78632E68
022EEA80
00000000

PSO EU V2

EU v2 Enable Code
1B7AAF61
8C5FF000
116F90D5
C0705040
1A87D212
40707044
1EEC10FE
0000D002
1EF4D0FE
2012D102
1E04D0FE
0009000B
1E14D0FE
AC937F78
1E24D0FE
0B50C4F3

EU v2 Server Code
0E0A0848
0001002C
002E301B
00000070
022E301C
642D6F73
022E3020
74612E63
022E3024
78632E68
022E3028
00000000