Starting from the current nightly build (and PyTorch 1.5 soon), for
Xbt[0, :, : , : ] = Xm.repeat(10, 1).view(10, 5, (3 + p))

we can write
using namespace torch::indexing;
Xbt.index_put_({ 0, Slice(), Slice(), Slice() }, Xm.repeat({ 10, 1 }).view({ 10, 5, (3 + p) }));

Here is the general translation for Tensor::index and Tensor::index_put_ functions:
Python             C++ (assuming `using namespace at::indexing`)
-------------------------------------------------------------------
0                  0
None               None
...                "..." or Ellipsis
:                  Slice()
start:stop:step    Slice(start, stop, step)
True / False       true / false
[[1, 2]]           torch::tensor({{1, 2}})