I've had a few inserted by others, Foley caths 4 times ( they inserted the first while I was knocked out for surgery, inserted 3 over the next week while I was awake.)
I've catheterized myself countless times with standard catheters, still do it occasionally due to middle-age BPH and a drug that causes further difficulty urinating - cath myself before long trips so I won't get suddenly caught more than 5-10 minutes from the restroom.
16 fr Bard cath (donated by a urologist, generics available on Amazon), tube of Surgilube (available on Amazon) - if the catheter isn't new out of the wrapper, always wash in soap and water, then rinse with alcohol inside and out, let dry for a few. Put a squirt of Surgilube on the tip of your penis, lube the catheter for almost its full length (I'm still amazed, it goes in close to a foot before mine works); these have a round bump on the far end and that needs to be facing UP while you insert, to keep the drain hole in the proper position once it reaches the bladder. SLOWLY insert into the penis -mildly uncomfortable. Some resistance and a feeling of a pinch when it passes through the prostate, 1-2 more inches and it's in the bladder and urine starts to flow. 3 to 15 seconds for the bladder to drain, and I get a feeling like someone's closed a door when it finally is drained and done. Slowly removed the tube, wash, dry, reuse again as needed. (I've never had a problem with infections, bleeding, etc - have had UTIs and prostatitis, but that was in my 20's way before any of this was started.) Not fun, but after the first couple times no big deal; just undress first since removing the catheter frequently causes drops or minor spills from what's still in the tube once removed.