Help with adding via heatsink using Eagle software

To start, I'd like to wish everyone a fabulous star studded happy New Year, & hoping we ALL see the tail end of #Covid19 SOON!

Also like to thank @dronebot-workshop (Bill) & everyone who's gone above & beyond to help me with various problems.

Speaking of problems, I'm building a parts carousel, as a way to store my parts, & to learn a little about Stepper Motors. I seem to have a LOT of parts.

I've created a board in Eagle, to step down a 24V LED power supply to 12V for the motor & 5V for the Arduino. I'm using a NEMA17 17HS15-1504S-X1, & am following along Bill's video of this.

The board uses two XL4015 & I've come unstuck trying to provide a heatsink for these using a pad underneath the board & a bunch of vias through to the top of the board underneath the SMD XL4015.

I've flipped the board over, & used the 'rect' command to draw a pad under the xl4015, which worked fine. My problem then is that I seem only to be able to add vias manually. I've been using fusion 360 for a year now, & have used 'patterns' to copy objects in the x & y coordinates, just be dragging the mouse & entering the number of copies, & or the spacing between them.

Eagle does NOT work in that way, I get an option widow that wants me to enter "Item Count", "X spacing" & "y spacing".

Do I really need to manually figure out these values, & have ZERO automation using the mouse? I tried this once, & somehow managed to get a bunch of vias at a 45deg angle, heading off the board into the ether.

Can anyone who uses Eagle give me a better way to do this? Should i use the 'polygon' command rather than the 'rectangle' command to draw the pad on the underside of the board. Can I change the size of the vias. I have so many questions, but have only managed to confuse myself thus far.

I'm including my board file if that helps anyone. Apparently I can't do that, so I'll attach an image of it.

Thanks,

Christine