Others will give a better answer than I will--but basically, when you reassemble the slide to the receiver,
1. Start with making sure that the barrel link is in the forward position.
2. Then, carefully slide the assembly on--and watch for the alignment of the link hole with the stop (receiver) hole.
3. Now, holding your slide stop so it is at a "5 o'clock" or so orientation, insert it and sweep it upwards, carefully, so you don't scratch the finish.
4. 'snap' into place--and it may help to have a little spatula (knife blade) on hand to push the stop plunger back so the stop goes into place.
And, the next time you have it apart, you may want to polish that stop a bit on the end to reduce the dreaded reassembly scratch.
There are literally a hundred or so good 3rd-party manuals on 1911 disassembly and reassembly--buy one. Perhaps a good one for a new 1911 owner would be Bill Wilson's booklet.
Jim H.