Wonderful reply! I would just emphasize/clarify that the HDR template (the DNA that you want to paste) doesn't actually get incorporated into the cell's genome. It merely serves as a guide, allowing the cell's repair machinery to copy the sequence info into the genome. I know you know this, but it's one of the most counterintuitive and easy-to-miss elements of the pathway.

For another entry-level resource on CRISPR everything, I would recommend CRISPRpedia - I've linked the "technology" page and it has an HDR section. But it also glosses over the it's-not-actually-pasted-in aspect that I addressed above. Even worse, this video shows something at 3:00 that simply does not happen (repair template being physically pasted into the genome).

This video does show an accurate depiction of the repair mechanism, with the good stuff starting at 1:00. Although this is not a CRISPR-specific video, the mechanism is very similar. Just think of the pink DNA as the repair template - the scientist-provided sequence-to-be-pasted. This is the single best resource I'm aware of that succinctly addresses the question posed by /u/AutomaticAd1918

OP, since you asked about how these things get into cells, you should check out the "Delivering CRISPR therapies" section of this CRISPRpedia page on genetic medicines. In brief, scientists can use viral vectors (widely used in gene therapy), lipid nanoparticles (same tech as COVID vaccines), or physical/mechanical means to get large molecules into cells. Although that page focuses on getting the CRISPR enzyme into a cell, the same approaches work for delivery of the HDR repair template (the DNA to be pasted). Delivery is a major challenge because cell membranes are fiercely dedicated to acting as a barrier, and they're very effective at preventing transit of larger molecules. Traditional small molecule drugs don't face the same delivery challenges because they can "slip through the cracks" and enter cells via diffusion.