That video isn't working..? Something about uploading and shenanigans.
Alright, I spent a good amount of time fighting Olimar's last time I went East, and spent a long time going toe to toe with our state's main Olimar player(The other Oli hardly plays). Like I've always said in the General Discussion, you have to watch the order of Olimar's Pikmin, and how they're used. Consider going into Training Mode and see how the order shifts when you do different moves, and how things like Oli's DSmash work. Keep an eye on how the whistle works as well.
If you're going to approach, you pretty much have to stick to dair and spaced bair's off a RAR. Landing Bair's will get you pivot grabbed, and if you must use dair, then do try to time your landing so both major hitboxes come out(Ending in air/landing hit box). It's flashy and can interrupt some shield grabs hilariously. Otherwise, you have to chase your fireballs in. High Risk, but you picked up Mario so what do you expect?
On the other side, you're gonna have to play some serious camping shenanigans to stay alive. Never allow yourself to be near Oli when he has a purple(unless you want to predict a Nair into his USmash). Cape and nair are going to be your Pikmin-away for the most part, with dair coming in a close third. I personally like nair more because your nair's weak hit on Oli's shield gives you just enough time to jab and interrupt his grab(Not sure about pivot grab. Probably not).
If I haven't sung it's praises enough, you have to learn to really think about using the RARJCUSmash. It's so fun, it's just a touch slower than your dash attack, but it's infinitely more useful for the most part, especially since it can be charged if you put the command in right in case you want to bait some spotdodges. This one is flashy, effective, and good anti air/pikmin. Be careful though- a shielded Usmash will get you shield grabbed. And that's no fun at all.
Try not to let Oli get a good advantageous stage, either. FD is pretty useless for us and Delfino works a lot better for Oli in this matchup because the main platform gives him x2 Purple chance and the sand/awnings/umbrellas give Oli those accursed Red Pikmin. He's really never at a loss against you on Delfino, regardless of platforms.
This'll be what you want to read when making your banning/stage striking decisions.
And do be careful. I've seen Oli's eat a fatal smash attack with the whistle just to punish your ending lag with a pikmin that'll kill quickly(Blue for grabs, Purple for USmash, etc...). He's likely to filter his pikmin the entire match, so keep an eye out for how he's filtering and work on exploiting whatever you can with what he has left.