Slow Motion in Library

Hello all and thanks for having me here!

I'm a long-term premiere pro user, that is tired of crashes, subscriptions, and slow workflows, trying to move to final cut. I recently bought an M1 mac mini that is amazing and start new projects in FCP. 
My problem is in premiere I can slow down my footage that is in 60 fps to 24 before I put my clips in a timeline I would like to know if there is a way to do this with the final cut, I mean I want to preview and select the sections of my clips already slows down to 24 fps. 
Thanks in advance and sorry for my bad English if you don't understand tell me and I will try to express myself better. 

You can do that, which I describe below. However in general FCP is so fast and it's so easy to adjust the timeline after inserting the clip, that I'd recommend just skimming the clip in the Event Browser, select the approx in/out points with the mouse or I and O keys, the insert that in the timeline with E (append to end) or W (insert at playhead or skimmer position), or drag/drop with mouse from Event Browser to timeline. Then in the timeline select the clip and use menu Modify>Retime>Automatic Speed. That will slow at 60 fps clip down to your timeline frame rate (24 fps). The timeline will automatically adjust without overwriting any clips. You can then trim the borders of the clip or hold down the T (Trim) key to slide the clip contents without affecting the duration.

If you really want to retime the clip in the Event Browser:

(1) Duplicate the clip with CMD+D (not required but likely a good idea)
(2) Open new clip via Clip>Open Clip. That opens it in a separate "timeline" but it's not a project
(3) Retime new clip with Modify>Retime>Slow>50% (for example)
(4) Press CMD+[ to go back in timeline history to previous timeline
(5) Verify your new clip at 50% speed is in the Event Browser and plays at 1/2 speed
(6) Pick In and Out points of slow down clip to insert into current timeline

FCP is very fast and efficient but to fully leverage this, please take the time to learn the "FCP way" of doing things. Here are some good tutorials:

Ripple Training 60 second quick tips: 

MacBreak Studio:  www.youtube.com/playlist?list=PL607BE2B2BFE9BE1A

DIY video tutorials for new FCP editors:  www.youtube.com/playlist?list=PLP6q-YgX0..._Fu_dXsr6Gt_IS26W1Sw

Hello Joema,

I'm training right now different ways to do the same thing that I did in premiere but from what I can understand to work in the final cut I need to see things from another point of view and I will do that.

Thanks for the time that you spend answering this topic I really appreciate it.

All the best for you