Meaning of 'to have at it'
"Octavia had been trimming the dead heads off the roses. She’d said they needed pruning back for the winter, and I’d told her to have at it. My grandmother had been the rose person in our household, and she hadn’t let me lay a finger on them unless they needed spraying for aphids. That had been one of my jobs."

It is in Chapter 18 of From Dead to Worse. Do you know what does it mean by ' to have at'? Moreover, can you provide another example, using this expression? Thanks.

Question

Meaning of 'to have at it'
"Octavia had been trimming the dead heads off the roses. She’d said they needed pruning back for the winter, and I’d told her to have at it. My grandmother had been the rose person in our household, and she hadn’t let me lay a finger on them unless they needed spraying for aphids. That had been one of my jobs."

It is in Chapter 18 of From Dead to Worse. Do you know what does it mean by ' to have at'? Moreover, can you provide another example, using this expression? Thanks.

Answer

"to have at it" means "one can do or try to do a task themselves"

"Baking an apple pie is very difficult. I don't think I can do this." said Elizabeth
"I think I could bake a delicious apple pie" said Annette
"Well, have at it Annette" said Elizabeth
(1 hour later)
"Thanks Annette! The pie tastes delicious!"

Answer

"Have at it" means "go ahead and do it".

Answer

To have at it means to start something.
"We're ready to start repairing the car.  Let's have at it." = Let's start the repairs.
"I have a plate of donuts for everybody.  Go ahead and have at it." = Go ahead and eat them.