grocery delivery

so I used Walmart's grocery delivery for the first time (getting it delivered between 5-6pm today). this is my first time using it as the whole family is sick & didnt want to go shopping sick. do they take delivery tip out of my debit card or do I give them money when they get here? I selected delivery tip on there but it's not showing up in my total. just want to make sure I get it right in case I use it again in the future!

it says delivery tip separately after delivery. will they give me a receipt to sign or do I need cash? I have cash just didnt know if some people are iffy about accepting it bc of COVID & me being sick. sorry if I'm overthinking this.