Yes you can take both.
Ashwagana is ideally taken before sleep with milk.
Arjunarishta is to be taken 15-20ml, mixed with equal amount of water, just after meals.
Next Steps
Ashwagandha powder can be take half to one tsp and if you like it in liquid form you can take ashwagandharishtam same as arjunarishta.
Better tak ein powder form before sleep with milk.
Health Tips
Avoid taking ashwagandha if you have bloating or indigestion issues.
Dont take arjunarishta empty stomach.