The Modlet tab is confusing, and I didn't realize it was still in. Modlets are available in any mod, using the Add More Mods button.
Under the Fun Pimps, install the Latest, then click on the Add New Mods button.
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The first sync can take a long time, depending on your computer and internet speed. You are best to Delete Downloads,, and do a Presync. Let it run until its done. Most times, it takes about 10 to 20 minutes, but I've heard people say its taken them an hour.