Please have a look at this thread: http://forum.mikrotik.com/t/configuring-ipsec-on-the-cisco-asa/138191/1 I believe that should be a good starting point in understanding the basics. For your situation, however, it is going to be more like a traditional road-warrior, not lan-to-lan VPN. So in comparison to what’s discussed in that thread you will have to use ‘tunnel-group type remote-access’ plus a whole bunch of RA-specific options (like address pool, split-tunnel configuration, etc) on your ASA, and then on Mikrotik side you will have to use dynamic policy generation and client side mode-config.
If looking through that thread does not help, then please post your full IPsec configuration from both ASA and Mikrotik. Again, I believe you should get an idea of what full IPsec config is by looking trough that other thread as well.