So, you have your content manager. Now, when you install content manager, you select a directory on your PC where you store your vita files.
For example: mine is C:\Vita --> in this folder will be the folders [music], [photos], [psvita] and [videos]
Here's my best explanation:
1. enter your [psvita] folder, then enter [PSAVEDATA]
2. from here there is another folder with gibberish in it: mine is [cf6cacf752052110]
3. after the gibberish folder, you should see the folder holding the savedata and exploit data. enter this folder (I use madblocker so mine [NPUZ00210CPMEM], yours will be different since it's Uno)
4. This folder is where you put ISOs and homebrew***
***EVERYTHING YOU PUT IN HERE TO INSTALL MUST BE IN CAPITAL LETTERS and only 8 characters long!
so, for instance, rename railgun something like RAIL.ISO (the extension .ISO has to be capitalized as well!)
5. Once you have everything in that directory that you want to install on the vita, connect the vita via usb to the pc and launch the content manager (on the PC and Vita).
6. navigate the content manager on the vita and select:
[PC --> PS Vita System]
Saved Data [PSP/Other]
And then select the Uno exploit and copy it over to the Vita. This will copy all the files you put in the exploit folder earlier including .ISO and .ZIP files