sidebar appears below the content

Depending on your theme, applying BP Template Pack may end up placing the sidebar and content wrappers at the same level than the header and the footer:

<div id="wrapper">
  <div id="header">...</div>
  <div id="content">...</div>
  <div id="sidebar">...</div>
  <div id="footer">...</div>
</div>

But you need them to be inside their own container. BP uses something like this:

<div id="header">...</div>
<div id="container">...</div>
  <div id="content">...</div>
  <div id="sidebar" role="complementary">...</div>
<div id="footer">...</div>

Your theme is probably using a different structure and/or container names from BP, for example:

<div id="wrapper">
  <div id="header">...</div>
  <div id="content">...</div>
    <div id="main">...</div>
    <div id="sidebar" class="col-right">...</div>
  <div id="footer">...</div>
</div>

or something like that. You need to check the structure of your theme in a page where your sidebar is displayed correctly, and then modify the template files BPTP copied to your theme to reflect that structure.

Here’s a nice tutorial (search is your friend): https://codex.buddypress.org/legacy/bp-template-pack-walkthrough-level-easy-2/