Using both a retinol product and this salicylic acid serum requires a very strategic approach to avoid damaging your skin barrier. The product guidance explicitly advises to "use with extra care if you already use retinoids or other peeling acids." Retinoids and salicylic acid are both active ingredients that accelerate skin cell turnover, and using them simultaneously can be overly harsh for most skin types.
The safest method is to alternate them. Do not apply them on the same night. For example, you could use the retinol cream on Monday and Thursday evenings, and the salicylic acid serum on Tuesday and Sunday evenings, with "rest" nights in between where you use only soothing, hydrating products. Another approach is to use them in different routines—retinol at night and the salicylic acid serum in the morning—but this increases daily exfoliation and sun sensitivity, making diligent sunscreen use even more critical.
Listen to your skin above all. Signs of overuse include persistent dryness, redness, stinging when applying other products, and increased sensitivity. If these occur, pause both actives for several days to allow recovery, then reintroduce them one at a time, spacing them further apart. When introducing any new active into an existing routine with another, start with a lower frequency for the new product than you normally would.