A few things:
1) Don't ollie onto the rail.
The trick to most street style rails is you're approaching from the side and very lightly popping onto them.
You're not aiming to land at the very top of the rail, rather you pop onto it from the side and land a little bit below the top section.
Here's a diagram/blog of what I mean (with equally amazing photoshop diagram): How To Properly Jump Onto Tall Street Style Snowboard Rails
It's actually REALLY easy to make it onto most rails when you realize you don't have to hop very high at all.
2) Hop over the entire rail a few times.
You can build up confidence by coming in from the side and instead of trying to land on the rail, hop over the entire thing and land on the other side.
This gets you used to the feeling of approaching and hopping onto the rail.
When you feel more comfortable after airing over the rail, you can just adjust your line and aim to start landing on the actual rail (remember to look at the end of the rail to get your approach correct if you want to make it all the way to the end).
3) Kinks are all about adjusting your body angle to match the rail.
The way to ride kinks is you have to be ready to adjust your body to match the angle of the rail as it changes. So as you reach each kink you need to correctly change your body angle less steep or more steep to match how the rail is changing.
If you can, find a flat-down box/rail to get used to the feeling of changing your body to match the changing angle before you try it on the down-flat-down rail.