Hi Anidup, I've taken a look at the EA mesh that you cloned and the mesh groups are as follows:
0 - the big shadow plane
1 - the small shadow planes under the tub feet and the pipe that comes out of the floor
2 - the shower curtain holder, shower curtain, and the pipe that comes out of the floor
3 - the tub, the tub faucet, and the shower head
4 - the water plane
In order for your item to look right and function correctly in the game you need to have a mesh group that corresponds to each of these mesh groups. Mesh group 2 and 3 can be mapped onto the same image if you want. If you do that you will need to import the same image to replace the 2 different images EA is using for mesh group 2 and mesh group 3. Even if your entire item is mapped to a single image the part of your item that represents the shower curtain holder, the shower curtain, and your shower pipe must all be in one mesh that you use to replace EA's mesh group 2 and the part of your item that represents the tub, the tub faucet, and your shower head must all be in a separate mesh that you use to replace EA's mesh group 3.
EA uses bone weighting to hook the mesh up to animations that are played when the Sim swooshes the shower curtain back and forth. This is how to see the bone weighting set up the item has:
1. Select the mesh group of interest in Object mode and switch to Edit mode.
2. Switch to smooth shading.
3. Type n on your keyboard to bring up the side bar menu and put a check in the box that says Show Weights.
4. Click the inverted triangle tab to bring up the Object Data section.
5. Click on the first bone in the Vertex Groups list. If you look at EA's mesh group 2 doing this you will see the shower curtain become rainbow colored.
The rainbow colors indicate bone weights. Wherever the curtain is dark blue the vertices in that section are not assigned to the bone you clicked on the Vertex Groups list. Wherever the curtain is bright red the vertices are 100% assigned to that bone. The color gradient between red and blue indicates a gradation of weighting so that the bright green indicates the vertices in that area are roughly 50% weighted to the selected bone. If you click the third bone on the list you will notice that the vertices that were partially weighted to the first bone on the list are also partially weighted to the third one too. Each vertex in the curtain mesh has a total of 100% weighting but some are weighted to two bones with the total weight divided between those bones equaling 100%. In order for your curtain to move like EA's curtain does you will need to recapitulate this weighting on your mesh.
There are a couple of ways you could approach this project. The first and easy way would be to select a different tub to clone. Your tub at this time does not have a shower and if you don't plan on adding one you would need to deal with that as well as the weighting issue if you continue on with the tub you've chosen. If, however, you select an EA tub that has no shower and no shower curtain you could still keep your shower curtain as an inanimate decorative part of your tub. This would get around the weighting issue because you would not have to weight the vertices.
The second and also easy way would be to use EA's mesh groups as-is except for deleting their tub mesh vertices and putting your tub in its place.
The third and more difficult way would be to match your shower curtain more closely to EA's shower curtain structure and transfer weights from it to yours. You would still need to deal with the fact that you're replacing a shower/tub combo with a tub alone unless you also add a shower head to your item. If you didn't add a shower the Sim will still get an option to take a shower and if the player picked that water would appear to be showering out of nowhere.
The fourth and most difficult way would be to attempt doing the weight paint yourself. Again, if you don't add a shower though you will still have shower water/animations unless you modify that element in the tuning.
