Since 2008 it PES still no stadium support for the Kitserver there is importing a stadium is not as simple as it looks PES6 times known.

Since no one can add new stadiums, it is necessary to replace existing stadiums.

For this, you can :

(1) Place them inside your Kitserver cv_1.img folder
(2) Import files using GGStudio or AFS Explorer to cv_1.img

For this you need to import files included in stadiums zip and rar files you have downloaded following this pattern :

Day/Summer ---- Texture_slot1.bin Stadium_slot1.bin
Day/Winter ---- Texture_slot2.bin Stadium_slot2.bin
Evening/Summer ---- Texture_slot3.bin Stadium_slot3.bin
Evening/Winter ---- Texture_slot4.bin Stadium_slot4.bin
Night/Summer ---- Texture_slot5.bin Stadium_slot5.bin
Night/Winter ---- Texture_slot6.bin Stadium_slot6.bin

According to this list of stadiums ( select the one you prefer to replace )

Trainings Platz
Day/Summer 45 47
Day/Winter 52 54
Evening/Summer 59 61
Evening/Winter 66 68
Night/Summer 73 75
Night/Winter 80 82

San Siro
Day/Summer 87 89
Day/Winter 94 96
Evening/Summer 101 103
Evening/Winter 108 110
Night/Summer 115 117
Night/Winter 122 124

Cataloni Satdium
Day/Summer 129 131
Day/Winter 136 138
Evening/Summer 143 145
Evening/Winter 150 152
Night/Summer 157 159
Night/Winter 164 166

Orange Arena
Day/Summer 171 173
Day/Winter 178 180
Evening/Summer 185 187
Evening/Winter 192 194
Night/Summer 199 201
Night/Winter 206 208

Stade Louis
Day/Summer 213 215
Day/Winter 220 222
Evening/Summer 227 229
Evening/Winter 234 236
Night/Summer 241 243
Night/Winter 248 250

Ville Marie
Day/Summer 255 257
Day/Winter 262 264
Evening/Summer 269 271
Evening/Winter 276 278
Night/Summer 283 285
Night/Winter 290 292

Bristol Mary
Day/Summer 297 299
Day/Winter 304 306
Evening/Summer 311 313
Evening/Winter 318 320
Night/Summer 325 327
Night/Winter 332 334

Mohamed Lewis
Day/Summer 339 341
Day/Winter 346 348
Evening/Summer 353 355
Evening/Winter 360 362
Night/Summer 367 369
Night/Winter 374 376

Konami Stadium
Day/Summer 381 383
Day/Winter 388 390
Evening/Summer 395 397
Evening/Winter 402 404
Night/Summer 409 411
Night/Winter 416 418

Stadio Olympico
Day/Summer 423 425
Day/Winter 430 432
Evening/Summer 437 439
Evening/Winter 444 446
Night/Summer 451 453
Night/Winter 458 460

Teatro Blanco
Day/Summer 465 467
Day/Winter 472 474
Evening/Summer 479 481
Evening/Winter 486 488
Night/Summer 493 495
Night/Winter 500 502

Bernabeu Stadium
Day/Summer 507 509
Day/Winter 514 516
Evening/Summer 521 523
Evening/Winter 528 530
Night/Summer 535 537
Night/Winter 542 544

Antlion Colosseum
Day/Summer 549 551
Day/Winter 556 558
Evening/Summer 563 565
Evening/Winter 570 572
Night/Summer 577 579
Night/Winter 584 586

Estadio da Luzii
Day/Summer 591 593
Day/Winter 598 600
Evening/Summer 605 607
Evening/Winter 612 614
Night/Summer 619 621
Night/Winter 626 628

Estadio Dragon
Day/Summer 633 635
Day/Winter 640 642
Evening/Summer 647 649
Evening/Winter 654 656
Night/Summer 661 663
Night/Winter 668 670

Estadio Jose de Alvalade
Day/Summer 675 677
Day/Winter 682 684
Evening/Summer 689 691
Evening/Winter 696 698
Night/Summer 703 705
Night/Winter 710 712

Thanks to SEI for this tips about importing stadiums