If you really want to try a Foley catheter, you don't need someone to insert it into you. In fact, if you are not absolutely certain that the person knows exactly what they are doing, a Registered Nurse for example, you may be better off self inserting it.
The reason is that you can feel pain if there is any problem you can stop instantly. By pain I mean ANYTHING more than a bit of discomfort. Also, you must resist the impulse to push just a little bit. A catheter should go in slowly and easily with no more than a bit of irritation.
Always use a prepackaged Foley catheterizing kit. It should be new and fully sterile, with an undamaged, unopened package, and in-date. Don't take chances.
There are some good videos on insertion on YouTube. ere is one: https://www.youtube.com/watch?v=VaTDB-Uq_Rw
A couple of hints:
If you don't know what size you need, a good starting point for an adult is Fr 14. Catheters come in many sizes. For most adults something in the range of Fr 12, Fr 14, Fr 16, or Fr 18. The Fr (French Scale) size is about 3x the catheter diameter in mm; a Fr 14 is about 4.7mm OD.
Foley catheters are mostly made of Latex (amber color) or Silicone (clear/white color). Generally silicone are a bit more expensive, but last longer. The Latex are generally a bit softer and can be more comfortable. Now there are also siliconized Latex too.
The catheter needs to be well lubricated with sterile jel. I prefer the kits with the lube in a syringe and inject the lube into the urethra before insertion. This is a personal choice.
If you have trouble getting the sterile gloves on and accidentally touch something non-sterile, you can wipe the gloves carefully with Betadine.
After a while, the catheter my irritate the entrance to your urethra a bit. If so, carefully clean the area and apply a bit of antibiotic ointment to lube the area.
Sleeping with a Foley in is a very nice experience. You can get a full night's sleep without waking, even once, to pee. It's likely there will be 1000ml or more in your pee bag in the morning.
In summary:
Be sterile
Be gentle
Don't continue if you have any pain
If in doubt.. STOP.
Enjoy