Lower volume in section of track

New to Reaper and not sure how to do this. I have about 2 measures I need to lower the volume in so it sits nicely with the rest of the mix. How do I isolate those measures and lower the volume? Thanks.

You can either split the track (put your cursor where you want to split and press the "s" key), before and after the section you want to effect. Now there is a line horizontally on the track, when you hover your cursor over it it will change to an up/down arrow and you can increase/decrease the volume. OR, click on the trm button and add an envelope (either volume or volume pre FX) the click on the line to add a node and then increase or decrease as needed.

Thanks 

Thanks Big Woody!