1. check current version
switch# show boot

2. show free space
switch# dir flash:

3. compare the size with the update image

4.(this step is optional) delete old files on the switch
switch# delete /f /r flash:[PATH]/[FILE]
or
switch# delete /f /r flash:[FILE]

5. load the update image via tfpt (Im using Solarwinds TFTP Server for this purpose)
for *.bin files: switch# tftp://[IP]/[PATH]/[UPDATEFILE] flash:
for *.tar files : switch# archive tar /xtract tftp://[IP]/[PATH]/[UPDATEFILE] flash:

6. verify the integrity (this step is optional)
switch# verify /md5 flash1:[UPDATEFILE]

7. change the boot path
switch# conf t
switch(config)# boot system flash:/[UPDATEFILE]
switch#show boot (zur Kontrolle)

8. save the config and reboot the switch
switch# wr mem
switch# reload