How to group an icon and an input element - html

Question

I'm trying to achieve the following:
Create 3 input elements in a row
Each should have a logo to the left of it, centered perfectly.
Each should have a border-bottom that spans the logo as well.
Like the following image:
However with my current code the images can't be centered and the border doesn't span them. Here's my code:
input {
border: none;
width: 250px;
background-color: #393d49;
border-bottom: 1px solid #767D93;
padding: 10px;
}
form img {
width: 24px;
height: 24px;
}
<form>
<img src="assets/images/envelope.png" alt="Envelope icon indicating user's E-Mail.">
<input type="email" placeholder="E-Mail"><br>
<img src="assets/images/locked.png" alt="Lock icon indicating user's Password.">
<input type="password" placeholder="Password"><br>
<img src="assets/images/avatar.png" alt="Avatar icon indicating user's Name.">
<input type="text" placeholder="Username"><br>
</form>

Answer 1

As it was suggested, I would also use the font-awesome library. But if your not comfortable with that idea, here is how you can do without.
form, .form-row, input {
background-color: #051024;
}
.input-icon, label, input {
display: inline-block;
}
form {
padding: 0.8em 1.2em;
}
.form-row {
padding: 0.8em 0;
padding-bottom: 0.2em;
}
.form-row:not(:last-child) {
border-bottom: solid #18273a 1px; /* Only the last row has a border */
}
.input-icon {
width: 15px;
height: 15px;
margin: 0 10px;
}
label {
max-width:4em; /* Or the maximum width you want your lebel to be */
min-width:4em; /* Same */
color:white;
font-weight: 100;
}
input {
border:none;
padding: 0.8em 0.5em;
color: #6691c9;
font-size: 15px;
outline: none; /* No glowing borders on chrome */
}
<form>
<div class="form-row">
<!-- Put your image here, like so -->
<img class="input-icon" src="http://1.bp.blogspot.com/-QTgDeozeWws/VLztRSNkMEI/AAAAAAAAKkQ/mrxdCfxWfvU/s1600/1f499.png" alt="oops"/>
<label for="form-email">Email</label>
<input id="form-email" type="email">
</div>
<div class="form-row">
<img class="input-icon" src="http://1.bp.blogspot.com/-QTgDeozeWws/VLztRSNkMEI/AAAAAAAAKkQ/mrxdCfxWfvU/s1600/1f499.png" alt="oops"/>
<label for="form-password">Password</label>
<input id="form-password"type="password" placeholder="(8 characters min)">
</div>
<div class="form-row">
<img class="input-icon" src="http://1.bp.blogspot.com/-QTgDeozeWws/VLztRSNkMEI/AAAAAAAAKkQ/mrxdCfxWfvU/s1600/1f499.png" alt="oops"/>
<label for="form-user">User</label>
<input id="form-user" type="text"><br>
</div>
</form>
If you're feeling adventurous
Try bootstrap, it has all you need to create cool web sites (it also includes the font-awesome library).