help with models

Well, did you make it in Blockbench? If not, use Blockbench.

Anyways, find it in your file explorer thing (no idea what it's called on your OS, but, for example, it's Finder on Macs). It should either be a .JSON (blocks/items), or a .JAVA (entities). Drag-and-drop it onto MCreator, just like with textures.

For blocks/items, a little thing will pop up asking you to set the texture mappings. Click on the box(es) and select the textures to use. (Make sure you've imported your textures before doing the model, and they all have to be "Block" textures, even if the model'll be for a custom item).

For entities, a little thing will pop up asking you to set the model animations (or you can click "Keep Current Animations").