VaporArt B*TTSTARD is a sweet coconut milk flavour. This Italian e-liquid has a PG/VG ratio of 30%PG/70%VG. It comes in 50ml bottles filled up to 60ml, so you have room for 10ml of base. The nicotine strength and the PG/VG ratio of the base that you will add will obviously affect the end result.
You need to add 10ml of base and shake well. Here are some possible combinations:
50ml Shortfill e-liquid + 10ml base 0mg/ml nicotine = 60ml e-liquid with 0mg/ml nicotine.
Shortfill e-liquid with 50ml + 10ml base 9mg/ml nicotine = 60ml e-liquid with 1.5mg/ml nicotine.
50ml Shake and Vape e-liquid + 10ml base 18mg/ml nicotine = 60ml e-liquid with 3mg/ml nicotine.